
[Federal Register Volume 88, Number 244 (Thursday, December 21, 2023)]
[Proposed Rules]
[Pages 88315-88336]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-27758]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[EPA-HQ-OW-2023-0222; FRL 10760-01-OW]
RIN 2040-AG30


Water Quality Standards To Protect Aquatic Life in the Delaware 
River

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: On December 1, 2022, the U.S. Environmental Protection Agency 
(EPA) determined that revised water quality standards are necessary to 
protect aquatic life in certain water quality management zones of the 
Delaware River. Specifically, the EPA issued an Administrator's 
Determination, pursuant to the Clean Water Act (CWA), finding that a 
revised designated use to protect aquatic life propagation and 
corresponding dissolved oxygen criteria to protect that use are 
necessary in Zone 3, Zone 4, and the upper portion of Zone 5 (in total, 
river miles 108.4 to 70.0) of the Delaware River. The CWA requires the 
EPA to publish proposed water quality standards following an 
Administrator's Determination. Thus, the EPA is proposing to promulgate 
an aquatic life designated use that includes propagation and protective 
water quality criteria for dissolved oxygen for Zone 3, Zone 4, and 
upper Zone 5 of the Delaware River.

DATES: Comments must be received on or before February 20, 2024. Public 
hearing: the EPA will hold two public hearings during the public 
comment period. Please refer to the SUPPLEMENTARY INFORMATION section 
for additional information on the public hearings.

ADDRESSES: You may send comments, identified by Docket ID No. EPA-HQ-
OW-2023-0222, by any of the following methods:
     Federal eRulemaking Portal: https://www.regulations.gov/ 
(our preferred method). Follow the online instructions for submitting 
comments.
     Mail: U.S. Environmental Protection Agency, EPA Docket 
Center, Office of Water Docket, Mail Code 28221T, 1200 Pennsylvania 
Avenue NW, Washington, DC 20460.
     Hand Delivery or Courier: EPA Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. 
The Docket Center's hours of operations are 8:30 a.m.-4:30 p.m., Monday 
through Friday (except Federal holidays).
    Instructions: All submissions received must include the Docket ID 
No. for this rulemaking. Comments received may be posted without change 
to https://www.regulations.gov/, including any personal information 
provided. For detailed instructions on sending comments and additional 
information on the rulemaking process, see the ``Public Participation'' 
heading of the SUPPLEMENTARY INFORMATION section of this document.

FOR FURTHER INFORMATION CONTACT: Hannah Lesch, Office of Water, 
Standards and Health Protection Division (4305T), Environmental 
Protection Agency, 1200 Pennsylvania Avenue NW, Washington, DC 20460; 
telephone number: (202) 566-1224; email address: [email protected].

SUPPLEMENTARY INFORMATION: This proposed rule preamble is organized as 
follows:

I. Public Participation
    A. Written Comments
    B. Participation in Public Hearings
II. General Information

[[Page 88316]]

    A. Does this action apply to me?
III. Background
    A. Statutory and Regulatory Authority
    B. Relevant Ecological History of the Delaware River
    C. Administration of Water Quality Standards in the Delaware 
River
    D. Currently Applicable Aquatic Life Designated Uses and 
Dissolved Oxygen Criteria
    E. Summary of the EPA's Administrator's Determination
IV. Proposed Water Quality Standards
    A. Scope of EPA's Proposed Rule
    B. Proposed Aquatic Life Designated Use
    C. Dissolved Oxygen Criteria To Protect Aquatic Life Propagation
V. Endangered Species Act Consultation
VI. Applicability
VII. Conditions Where Federal Water Quality Standards Would Not Be 
Promulgated or Would Be Withdrawn
    A. Conditions Where Federal Standards Would Not Be Promulgated
    B. Conditions Where Federal Standards Would Be Withdrawn
VIII. Alternative Regulatory Approaches and Implementation 
Mechanisms
    A. Water Quality Standards Variances
    B. NPDES Permit Compliance Schedules
    C. Clean Water Act Section 303(d)/305(b) Water Quality 
Assessments
IX. Economic Analysis
X. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 14094: Modernizing Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect 
Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA)
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations and Executive Order 14096: Revitalizing Our Nation's 
Commitment to Environmental Justice for All

I. Public Participation

A. Written Comments

    Submit your comments, identified by Docket ID No. EPA-HQ-OW-2023-
0222, at https://www.regulations.gov (the EPA's preferred method), or 
the other methods identified in the ADDRESSES section. Once submitted, 
comments cannot be edited or removed from the docket. The EPA may 
publish any comment received to its public docket. Do not submit to the 
EPA's docket at https://www.regulations.gov any information you 
consider to be Confidential Business Information (CBI), Proprietary 
Business Information (PBI), or other information whose disclosure is 
restricted by statute. Multimedia submissions (audio, video, etc.) must 
be accompanied by a written comment. The written comment is considered 
the official comment and should include discussion of all points you 
wish to make. The EPA will generally not consider comments or comment 
contents located outside of the primary submission (i.e., on the web, 
cloud, or other file sharing system). Please visit https://www.epa.gov/dockets/commenting-epa-dockets for additional submission methods; the 
full EPA public comment policy; information about CBI, PBI, or 
multimedia submissions; and general guidance on making effective 
comments.

B. Participation in Public Hearings

    The EPA is offering two public hearings so that interested parties 
may also provide oral comments on this proposed rulemaking. For more 
details on the public hearings and to register to attend the hearings, 
please visit https://www.epa.gov/wqs-tech/water-quality-standards-delaware-river.

II. General Information

A. Does this action apply to me?

    A range of individuals and entities could be affected by this 
rulemaking, if finalized. For example, entities that discharge 
pollutants to certain waters under the jurisdiction of the states of 
Delaware, New Jersey, and Pennsylvania--such as industrial facilities 
and municipalities that manage stormwater, separate sanitary, or 
combined sewer systems--could be indirectly affected by this rulemaking 
because Federal water quality standards (WQS) promulgated by the EPA 
would be the applicable WQS for these waters for CWA purposes (Table 1 
of this preamble). Specifically, these WQS would be the applicable 
standards that must be used in CWA regulatory programs, such as 
permitting under the National Pollutant Discharge Elimination System 
(NPDES) under CWA section 402 \1\ and identifying impaired waters under 
CWA section 303(d). In addition, individuals and entities who rely on 
or benefit from aquatic life in those waters may be indirectly 
affected.
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    \1\ Before any water quality-based effluent limit would be 
included in an NPDES permit, the permitting authority (here, the 
states of Delaware, New Jersey, and Pennsylvania), must first 
determine whether a discharge ``will cause or has the reasonable 
potential to cause, or contribute to an excursion above any WQS.'' 
40 CFR 122.44(d)(1)(i) and (ii).

      Table 1--Entities Potentially Affected by This Proposed Rule
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                                      Examples of potentially affected
             Category                             entities
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Industry..........................  Industrial point sources discharging
                                     to certain waters in Delaware, New
                                     Jersey, and Pennsylvania.
                                     Commercial fishing operations that
                                     harvest fish.
Municipalities, including those     Publicly owned treatment works or
 with stormwater or combined sewer   similar facilities responsible for
 system outfalls.                    managing stormwater, separate
                                     sanitary, or combined sewer systems
                                     that discharge to certain waters in
                                     Delaware, New Jersey, and
                                     Pennsylvania.
Recreation and Tourism............  Anglers and tourists seeking
                                     recreational opportunities related
                                     to aquatic life in certain waters
                                     in Delaware, New Jersey, and
                                     Pennsylvania.
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    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities that could be indirectly affected 
by this action. If you have questions regarding the applicability of 
this action to a particular entity, consult the person listed in the 
FOR FURTHER INFORMATION CONTACT section above.

III. Background

A. Statutory and Regulatory Authority

    CWA section 101(a)(2) establishes a national goal of ``water 
quality which provides for the protection and propagation of fish, 
shellfish, and wildlife, and provides for recreation in and on the 
water'' (hereafter, collectively referred to as ``101(a)(2) uses'' or 
``101(a)(2) goals''), wherever attainable. The EPA's regulation at 40 
CFR 131.10(g) implements this statutory

[[Page 88317]]

provision by requiring that WQS protect 101(a)(2) uses unless those 
uses are shown to be unattainable.
    Under the CWA, states have the primary responsibility for 
reviewing, establishing, and revising WQS applicable to their waters 
(CWA section 303(c)). WQS define the desired condition of a water body, 
in part, by designating the use or uses to be made of the water and by 
setting the numeric or narrative water quality criteria to protect 
those uses (40 CFR 131.2, 131.10, and 131.11). There are two primary 
categories of water quality criteria: human health criteria and aquatic 
life criteria. Human health criteria protect designated uses such as 
public water supply, recreation, and fish and shellfish consumption. 
Aquatic life criteria protect designated uses such as protection and 
propagation of fish, invertebrates, and other aquatic species. 
Regardless of their category, water quality criteria ``must be based on 
sound scientific rationale and must contain sufficient parameters or 
constituents to protect the designated use. For waters with multiple 
use designations, the criteria shall support the most sensitive use'' 
(40 CFR 131.11(a)(1)).
    States are required to hold a public hearing to review applicable 
WQS at least once every three years and, if appropriate, revise or 
adopt new standards (CWA section 303(c)(1); 40 CFR 131.20(a)). Every 
three years, states must also reexamine water body segments that do not 
include the 101(a)(2) uses to determine if new information has become 
available that indicates the 101(a)(2) uses are attainable, and if so, 
revise the WQS accordingly (40 CFR 131.20(a)). Any new or revised WQS 
must be submitted to the EPA for review and approval or disapproval 
(CWA section 303(c)(2)(A) and (c)(3)).
    CWA section 303(c)(4)(B) independently authorizes the Administrator 
to determine that a new or revised standard is necessary to meet CWA 
requirements; this action is frequently referred to as an 
``Administrator's Determination.'' Pursuant to CWA section 
303(c)(4)(B), after making an Administrator's Determination, the EPA 
must propose and promulgate WQS specified in the Administrator's 
Determination. If a state adopts and the EPA approves WQS that address 
the Administrator's Determination prior to the EPA's promulgation, then 
the EPA would no longer be required to promulgate WQS.

B. Relevant Ecological History of the Delaware River

    The Delaware River has historically been home to numerous species 
of ecological, recreational, and economic importance; however, 
centuries of anthropogenic water quality impacts and habitat 
degradation, peaking in the mid-twentieth century, made portions of the 
river unsuitable for many aquatic species. In the 1700s and 1800s, many 
native fish species in the Delaware River faced declining populations 
due to overharvesting and the installation of physical barriers that 
prevented fish passage.\2\ Further population declines of native 
oxygen-sensitive species--such as the Atlantic Sturgeon (Acipenser 
oxyrinchus oxyrinchus), American Shad (Alosa sapidissima), Shortnose 
Sturgeon (Acipenser brevirostrum), and Striped Bass (Morone saxatilis), 
among others \3\--were linked to accelerating degradation of water 
quality through the first half of the 1900s, including seasonal anoxia 
(i.e., absence of oxygen) by the mid-twentieth century in Zone 3, Zone 
4, and the upper portion of Zone 5 of the Delaware River.\4\
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    \2\ Hardy, C.A. (1999). Fish or Foul: A History of the Delaware 
River Basin Through the Perspective of the American Shad, 1682 to 
the Present. Pennsylvania History, 66(4), 506-534. https://digitalcommons.wcupa.edu/hist_facpub/13; Secor, D.H. and Waldman, J. 
(1999). Historical abundance of Delaware Bay Atlantic sturgeon and 
potential rate of recovery. American Fisheries Society Symposium. 
23. 203-216. https://www.researchgate.net/publication/291783957_Historical_abundance_of_Delaware_Bay_Atlantic_sturgeon_and_potential_rate_of_recovery; Smith, T.I.J., & Clugston, J.P. (1997) 
Status and management of Atlantic sturgeon, Acipenser oxyrinchus, in 
North America. Environmental Biology of Fishes 48, 335-346. https://doi.org/10.1023/A:1007307507468; National Marine Fisheries Service. 
(1998). Recovery Plan for the Shortnose Sturgeon (Acipenser 
brevirostrum). Prepared by the Shortnose Sturgeon Recovery Team for 
the National Marine Fisheries Service, Silver Spring, Maryland. 104 
pages. https://repository.library.noaa.gov/view/noaa/15971.
    \3\ Stoklosa, A.M., Keller, D.H., Marano, R., and Horwitz, R.J. 
(2018). ``A Review of Dissolved Oxygen Requirements for Key 
Sensitive Species in the Delaware Estuary.'' Academy of Natural 
Sciences of Drexel University. November 2018. https://www.nj.gov/drbc/library/documents/Review_DOreq_KeySensSpecies_DelEstuary_ANStoDRBCnov2018.pdf.
    \4\ See citations in footnote 2 of this preamble; Atlantic 
States Marine Fisheries Commission. (1981). Interstate Fisheries 
Management Plan for the Striped Bass. http://www.asmfc.org/uploads/file/1981FMP.pdf.
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    Dissolved oxygen is an important water quality parameter that can 
significantly influence the distribution and abundance of aquatic 
organisms and ecological relationships in aquatic ecosystems. Aquatic 
organisms need to obtain adequate levels of dissolved oxygen to 
maintain and support normal functioning, including during sensitive 
life stages, such as spawning, larval development, and juvenile 
growth.\5\ As dissolved oxygen levels decrease in a waterbody, the rate 
at which aquatic organisms can obtain oxygen from the water decreases, 
resulting in impaired growth and reduced survival. Maintaining a 
healthy ecosystem requires dissolved oxygen levels above thresholds 
that impair growth and survival of aquatic species.
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    \5\ United States Environmental Protection Agency. (2021). 
Factsheet on Water Quality Parameters: Dissolved Oxygen. July 2021. 
Document ID: EPA 841F21007B. https://www.epa.gov/system/files/documents/2021-07/parameter-factsheet_do.pdf; United States 
Environmental Protection Agency. (2023a). Indicators: Dissolved 
Oxygen. June 9, 2023. https://www.epa.gov/national-aquatic-resource-surveys/indicators-dissolved-oxygen.
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1. Causes of Low Dissolved Oxygen in the Specified Zones of the 
Delaware River
    Discharges of untreated or poorly treated municipal and industrial 
wastewater into the specified zones of the Delaware River have 
historically been a major cause of water quality degradation, including 
oxygen depletion.\6\ While conditions have significantly improved, 
inputs of oxygen-consuming wastes from wastewater dischargers, 
especially ammonia (NH3) and ammonium (NH4\+\) 
(which in combination are hereafter referred to as ``ammonia 
nitrogen''), as well as sediment-water ammonium flux and sediment 
oxygen demand continue to be significant sources of oxygen demand in 
the specified zones of the Delaware River.\7\
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    \6\ Hardy (1999); Delaware River Basin Commission. (2022a). 
Analysis of Attainability: Improving Dissolved Oxygen and Aquatic 
Life Uses in the Delaware River Estuary. September 2022 Draft. See 
section 3--``Factors that can Improve Dissolved Oxygen in the Fish 
Maintenance Area.'' https://www.nj.gov/drbc/library/documents/AnalysisAttainability/AnalysisAttainability_DRAFTsept2022.pdf.
    \7\ Delaware River Basin Commission. (2022b). Modeling 
Eutrophication Processes in the Delaware River Estuary--Three-
Dimensional Water Quality Model. https://www.nj.gov/drbc/library/documents/AnalysisAttainability/WQModelCalibrationRpt_DRAFTsept2022.pdf.
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    Along the Delaware River, untreated wastewater discharges typically 
occur during and after rainfall due to combined sewer overflows (CSOs), 
which are a source of nutrients (i.e., nitrogen and phosphorus), 
sediments, and toxic contaminants, and can lead to increased chemical 
and biological oxygen demand in the river.\8\ Although the cumulative 
impact of historical

[[Page 88318]]

CSOs on sediment oxygen demand in the Delaware River has not been 
estimated, CSOs can over time increase or maintain sediment oxygen 
demand as untreated organic material settles on the riverbed and is 
broken down by oxygen consuming bacteria (thus, removing oxygen from 
the water column), a process that continues long after the end of an 
overflow event.\9\ CSOs have been a persistent source of pollutants in 
the specified zones of the Delaware River for over a century. For 
example, sewer overflows from Philadelphia in the early 1900s deposited 
over 200,000 tons of solids per year, which, in combination with other 
solid wastes, created deposits 12 feet deep in the river.\10\ From July 
1, 2021, to June 30, 2022, Philadelphia's wastewater system alone 
discharged over 1.7 billion cubic feet of CSOs into the Delaware 
River.\11\
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    \8\ Miskewitz, R. and Uchrin, C. (2013). In-Stream Dissolved 
Oxygen Impacts and Sediment Oxygen Demand Resulting from Combined 
Sewer Overflow Discharges. Journal of Environmental Engineering, 
139(10). https://doi.org/10.1061/(ASCE)EE.1943-7870.0000739.
    \9\ Miskewitz and Uchrin (2013).
    \10\ Hardy (1999).
    \11\ Philadelphia Water Department. (2022). Combined Sewer 
Management Program Annual Report. Stormwater Management Program 
Annual Report. See Appendix D--``NPDES Annual CSO Status Report FY 
2022,'' Table 2--``Overflow Summary for 7/1/2021-6/30/2022.'' 
https://water.phila.gov/pool/files/fy22-npdes-annual-report.pdf.
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    Although most point source discharges today are treated, treated 
effluent can still contain high levels of ammonia nitrogen, which 
depletes oxygen in the water as bacteria oxidize ammonia into nitrite, 
nitrate and dinitrogen gas.\12\ During the reporting periods from July 
through October 2022, major wastewater treatment facilities along the 
Delaware River discharged ammonia nitrogen at monthly average 
concentrations ranging from a low of 0.07 milligrams nitrogen per liter 
(mg-N/L) at the Florence Township Sewage Treatment Plant in New Jersey 
(discharging into Zone 2 of the Delaware River) to a high of 35 mg-N/L 
at the Camden County Municipal Utilities Authority in New Jersey 
(discharging into Zone 3 of the Delaware River).\13\
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    \12\ United States Environmental Protection Agency. (2023b). 
Ammonia. https://www.epa.gov/caddis-vol2/ammonia.
    \13\ Each individual reporting period is one month long. For the 
reporting period ending on September 30, 2022, Florence Township 
Municipal Building discharged an average of .07 mg/L of ammonia. For 
the reporting period ending on July 31, 2022, Camden County 
Municipal Utilities Authority discharged an average of 35 mg/L of 
ammonia. Source: U.S. Environmental Protection Agency. Integrated 
Compliance Information System (ICIS). Database. Retrieved June 29, 
2023.
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2. Endangered Species in the Specified Zones of the Delaware River
    The Delaware River is home to two oxygen-sensitive fish species--
Shortnose Sturgeon and Atlantic Sturgeon--that are protected under the 
Federal Endangered Species Act (ESA). All populations of Shortnose 
Sturgeon were listed as endangered in 1967.\14\ Across the U.S., 
Shortnose Sturgeon face ongoing threats due to water pollution, habitat 
degradation, and fisheries bycatch, among other factors.\15\ While the 
historic population size of Shortnose Sturgeon in the Delaware River 
remains unknown, in 2006 the population was estimated to be 
approximately 12,000 adults.\16\ The New York Bight distinct population 
segment (DPS) of Atlantic Sturgeon--which includes the population found 
in the Delaware River--was listed as endangered under the ESA in 
2012.\17\ In 2017, the National Oceanic and Atmospheric Administration 
(NOAA Fisheries) designated the Delaware River, among others, as 
critical habitat for the New York Bight DPS of Atlantic Sturgeon,\18\ 
and reaffirmed its endangered listing in 2022 following a five-year 
review of its status.\19\ The remnant population of the New York Bight 
DPS of Atlantic Sturgeon faces ongoing threats due to water quality in 
natal rivers, such as the Delaware River, as well as climate change, 
ship strikes, fisheries bycatch, habitat loss, and entanglement in 
fishing gear.20 21 Like the Shortnose Sturgeon, the historic 
population size of Atlantic Sturgeon is not well documented. However, 
in 1890, when the population was already declining, there were 
approximately 180,000 female Atlantic Sturgeon in the Delaware 
River.\22\ Despite improvements in dissolved oxygen levels since the 
1970s, it is estimated that only 125-250 adult Atlantic Sturgeon 
currently return to spawn in the Delaware River.\23\
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    \14\ Federal Register, Vol. 32, No. 48 (32 FR 4000). March 11, 
1967. https://www.fisheries.noaa.gov/s3//2022-12/4000-4002.pdf.
    \15\ NOAA Fisheries. (2023a). Shortnose Sturgeon--Overview. 
https://www.fisheries.noaa.gov/species/shortnose-sturgeon.
    \16\ Id.; NOAA Fisheries. (2023b). Shortnose Sturgeon--
Populations. https://www.fisheries.noaa.gov/species/shortnose-sturgeon#populations.
    \17\ Federal Register, Vol. 77, No. 24. February 6, 2012. 77 FR 
5879. https://www.federalregister.gov/documents/2012/02/06/2012-1946/endangered-and-threatened-wildlife-and-plants-threatened-and-endangered-status-for-distinct.
    \18\ Federal Register, Vol. 82, No. 158 (82 FR 39160). August 
17, 2017. 50 CFR part 226. https://www.federalregister.gov/documents/2017/08/17/2017-17207/endangered-and-threatened-species-designation-of-critical-habitat-for-the-endangered-new-york-bight.
    \19\ National Marine Fisheries Service. (2022). New York Bight 
Distinct Population Segment of Atlantic Sturgeon (Acipenser 
oxyrinchus oxyrinchus), 5-Year Review: Summary and Evaluation. 
February 17, 2022. https://www.fisheries.noaa.gov/resource/document/new-york-bight-distinct-population-segment-atlantic-sturgeon-5-year-review.
    \20\ Ibid. See Section 2.3.2, ``Five-Factor Analysis (threats, 
conservation measures, and regulatory mechanisms)'', A. through E., 
pp. 14-25.
    \21\ Dunton, K.J., Jordaan, A., Conover, D.O., McKown, K.A., 
Bonacci, L.A., and Frisk, M.G. (2015). Marine Distribution and 
Habitat Use of Atlantic Sturgeon in New York Lead to Fisheries 
Interactions and Bycatch. Marine and Coastal Fisheries 7:18-32. 
https://doi.org/10.1080/19425120.2014.986348; Atlantic Sturgeon 
Bycatch Working Group. (2022). Action Plan to Reduce Atlantic 
Sturgeon Bycatch in Federal Large Mesh Gillnet Fisheries. NOAA 
National Marine Fisheries Service. https://media.fisheries.noaa.gov/2022-09/Final-Action-Plan-to-Reduce-Atlantic-Sturgeon-Bycatch.pdf.
    \22\ Secor and Waldman (1999).
    \23\ White, S.L., Sard, N.M., Brundage, H.M., Johnson, R.L., 
Lubinski, B.A., Eackles, M.S., Park, I.A., Fox, D.A., and Kazyak, 
D.C. (2022). Evaluating Sources of Bias in Pedigree-Based Estimates 
of Breeding Population Size. Ecological Applications 32(5): e2602. 
https://doi.org/10.1002/eap.2602.
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    In addition to being listed as endangered under the ESA, available 
evidence suggests that Shortnose Sturgeon and Atlantic Sturgeon are the 
most oxygen-sensitive species in the specified zones of the Delaware 
River. In general, all sturgeon species share common life history 
traits,\24\ among which they are recognized to be relatively more 
sensitive to low dissolved oxygen levels compared to other co-occurring 
fish.25 26 Sturgeons are considered unusually sensitive to 
hypoxia given their documented metabolic and behavioral responses and 
limited ability to oxyregulate.\27\ Juvenile Atlantic Sturgeon are 
particularly sensitive to low dissolved oxygen levels, especially at 
high water temperatures,\28\ such as those typically present at the 
peak of summer in the Delaware River.\29\ A literature review across 
oxygen-

[[Page 88319]]

sensitive species in the Delaware River indicates that Atlantic 
Sturgeon, particularly the juvenile life stage, have the highest 
documented dissolved oxygen requirements for growth and survival when 
compared to other oxygen-sensitive species in the specified zones of 
the Delaware River.\30\ In its five-year review of the listing of the 
New York Bight DPS of Atlantic Sturgeon, NOAA Fisheries observed a 
continuation of low dissolved oxygen conditions in the Delaware River 
around the expected location of age 0-1 Atlantic Sturgeon.\31\ Low 
oxygen levels can lead to habitat displacement effects whereby juvenile 
Atlantic Sturgeon seeking relief are constrained to waters that remain 
suboptimal for growth due to other limiting factors (e.g., higher 
salinity waters).\32\ NOAA Fisheries also noted studies linking age 0-1 
Atlantic Sturgeon capture rates in the fall to the preceding summer 
dissolved oxygen conditions in the Delaware River, providing further 
evidence that low dissolved oxygen levels are a contributor to the 
mortality of juvenile Atlantic Sturgeon.\33\
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    \24\ Federal Register, Vol. 82, No. 158 (82 FR 39161). August 
17, 2017. 50 CFR part 226. pp. 39161-39163. https://www.federalregister.gov/documents/2017/08/17/2017-17207/endangered-and-threatened-species-designation-of-critical-habitat-for-the-endangered-new-york-bight.
    \25\ Ibid. p. 39162, see Dees (1961), Sulak and Clugston (1999), 
Billard and Lecointre (2001), Secor and Niklitschek (2002), and 
Pikitch et al. (2005), cited therein.
    \26\ Stoklosa et al. (2018) ; Secor, D.H. and Niklitschek, E.J. 
(2001). Hypoxia and Sturgeons: Report to the Chesapeake Bay Program 
Dissolved Oxygen Criteria Team. March 29, 2001.Reference Number: 
[UMCES] CBL 01-0080. https://www.researchgate.net/publication/277065759_Hypoxia_and_Sturgeons_report_to_the_Chesapeake_Bay_Program_Dissolved_Oxygen_Criteria_Team.
    \27\ Secor and Niklitschek (2001). Oxyregulation refers to an 
organism's ability to maintain metabolic rates as the oxygen level 
in the water declines.
    \28\ Secor, D., and T. Gunderson. (1998). Effects of hypoxia and 
temperature on survival, growth, and respiration of juvenile 
Atlantic sturgeon, Acipenser oxyrinchus. Fishery Bulletin 96:603-
613.; Niklitschek, E. (2001). Bioenergetics modeling and assessment 
of suitable habitat for juvenile Atlantic and shortnose sturgeons 
(Acipenser oxyrinchus and A. brevirostrum) in the Chesapeake Bay. 
University of Maryland at College Park.
    \29\ More information is available in the associated document, 
Technical Support Document for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River.
    \30\ Stoklosa et al. (2018).
    \31\ National Marine Fisheries Service (2022). See Section 
2.3.2.1, ``Present or threatened destruction, modification, or 
curtailment of its habitat or range.''
    \32\ Ibid. See Allen et al. (2014), cited therein.
    \33\ Ibid. See Moberg and DeLucia (2016), Stetzar et al. (2015), 
and Park (2020), cited therein.
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3. Dissolved Oxygen Trends in the Specified Zones of the Delaware River
    Dissolved oxygen levels in Zone 3, Zone 4, and the upper portion of 
Zone 5 of the Delaware River mirror trends in historic pollutant 
loading and recent pollution control efforts in the river. Average 
summer dissolved oxygen levels in the Delaware River near Chester, 
Pennsylvania (Zone 4) declined from near saturation in the late 1880s 
to near zero (i.e., anoxia) in the 1950s and 1960s.\34\ Starting in 
1970, dissolved oxygen levels began to increase steadily in association 
with declining ammonia nitrogen concentrations in the river.\35\ 
Reductions in nutrient concentrations, including ammonia nitrogen, have 
been documented across the Delaware River watershed through at least 
2018.\36\ However, dissolved oxygen levels in the summer remain low 
enough to limit the growth and survival of oxygen-sensitive species and 
life stages, such as juvenile Atlantic Sturgeon.\37\ Recent modeling 
studies have shown that further reductions in pollutant loading, 
including a reduction in the volume and frequency of CSOs as well as 
enhanced treatment of ammonia nitrogen discharges, could significantly 
improve the dissolved oxygen conditions in the relevant zones of the 
Delaware River.\38\
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    \34\ Sharp, J. (2010). Estuarine oxygen dynamics: What can we 
learn about hypoxia from long-time records in the Delaware estuary? 
Limnology and Oceanography, 55(2), 535-548.
    \35\ Sharp (2010).
    \36\ Shoda, M.E., and Murphy, J.C. (2022). Water-quality trends 
in the Delaware River Basin calculated using multisource data and 
two methods for trend periods ending in 2018. U.S. Geological Survey 
Scientific Investigations Report 2022-5097. https://doi.org/10.3133/sir20225097.
    \37\ More information is available in the associated document, 
Technical Support Document for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River; Delaware 
River Basin Commission (2022a); Niklitschek, E., and D. Secor. 
(2009a). Dissolved oxygen, temperature and salinity effects on the 
ecophysiology and survival of juvenile Atlantic sturgeon in 
estuarine waters: I. Laboratory results. Journal of Experimental 
Marine Biology and Ecology 381:S150-S160. https://doi.org/10.1016/j.jembe.2009.07.018; Stoklosa et al. (2018).
    \38\ Delaware River Basin Commission (2022a, 2022b).
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C. Administration of Water Quality Standards in the Delaware River

    In 1961, the Delaware River Basin Compact established the Delaware 
River Basin Commission (DRBC), comprised of the states of Delaware, New 
Jersey, New York,\39\ and Pennsylvania and the Federal Government, to 
jointly manage the Delaware River Basin's water resources.\40\ Through 
DRBC, each state participates in the shared governance of this regional 
resource and maintains sovereign rights over the portion of the river 
within its jurisdiction.\41\
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    \39\ Although portions of the Delaware River Estuary are within 
New York's jurisdiction, the EPA's proposed rulemaking is not 
applicable to waters under New York's jurisdiction (see section 
IV.A. of this preamble: Scope of EPA's Proposed Rule). Therefore, 
the EPA does not discuss New York's WQS further in this proposed 
rulemaking.
    \40\ DRBC was established pursuant to Federal law (75 Stat. 688 
(1961)).
    \41\ Delaware River Basin Compact, art. 1, ``Short Title, 
Definitions, Purpose and Limitations,'' Sec.  1.3(a), (b), & (c) 
``Purpose and Findings,'' pp. 3 & 4, and art. 5, ``Pollution 
Control,'' Sec.  5.5(b), ``Further Jurisdiction,'' p. 11, (1961), 
available at https://www.nj.gov/drbc/library/documents/compact.pdf.
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    Pursuant to the Delaware River Basin Compact, DRBC adopts WQS for 
interstate waters, including the Delaware River Estuary.\42\ However as 
noted above, under the CWA, states have the primary responsibility for 
reviewing, establishing, and revising WQS applicable to their waters, 
and must submit new or revised WQS to the EPA for review and approval 
or disapproval.
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    \42\ Delaware River Basin Compact, art. 5, ``Pollution 
Control,'' Sec.  5.2, ``Policy and Standards,'' p. 11 (1961), 
available at https://www.nj.gov/drbc/library/documents/compact.pdf 
(DRBC ``may adopt and from time to time amend and repeal rules, 
regulations and standards to control . . . future pollution and 
abate existing pollution''). DRBC, the states, and the EPA refer to 
these rules, regulations, and standards as equivalent to WQS under 
the CWA. As such, the term WQS is used herein to refer to these 
rules, regulations, and standards.
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    Given the unique interjurisdictional management of the Delaware 
River Estuary, WQS are submitted to the EPA for review through a 
process coordinated across the state, regional, and Federal levels. 
This process begins when DRBC adopts WQS for the Delaware River 
Estuary. To comply with CWA section 303(c), the Estuary states of 
Delaware, New Jersey, and Pennsylvania have provisions in their state 
WQS regulations that explicitly reference or implicitly incorporate 
DRBC's WQS as the applicable WQS for the portions of the river under 
their jurisdictions. When DRBC adopts new or revised WQS, each relevant 
member state submits a certification to the EPA from that state's 
attorney general or other appropriate legal authority, in accordance 
with 40 CFR 131.6(e). Those certifications provide that DRBC's new or 
revised WQS were duly adopted pursuant to state law. The EPA then 
reviews whether those WQS are consistent with the CWA and the EPA's 
implementing regulation and approves or disapproves them.

D. Currently Applicable Aquatic Life Designated Uses and Dissolved 
Oxygen Criteria

    In 1967, DRBC adopted WQS for the zones of the Delaware River 
included in this proposed rule.\43\ Based on the conditions of the 
Delaware River at the time, DRBC concluded that ``propagation of fish'' 
was not attainable for Zone 3, Zone 4, and the upper portion of Zone 5 
(in total, river miles 108.4 to 70.0) of the Delaware River (hereafter, 
referred to as ``specified zones'' or ``relevant zones''),\44\ due to 
the presence of industrial and municipal discharges and associated low 
dissolved oxygen levels. DRBC, therefore, adopted WQS to include 
``maintenance of resident fish and other aquatic life,'' ``passage of 
anadromous fish,'' and a dissolved oxygen criterion of 3.5 mg/L, as a 
daily average, for these

[[Page 88320]]

zones of the Delaware River.45 46 Because these WQS provide 
for the ``maintenance'' and ``passage'' of aquatic life (i.e., 
``protection'') but not the ``propagation of fish, shellfish and 
wildlife,'' these WQS are not consistent with the goals specified in 
CWA section 101(a)(2). However, these WQS adopted in 1967 remain 
applicable for Zone 3, Zone 4, and the upper portion of Zone 5 of the 
Delaware River as directly referred to or implicitly incorporated in 
Delaware's, New Jersey's, and Pennsylvania's WQS.
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    \43\ Delaware River Basin Commission. (2013). Delaware River 
Basin Water Code. https://www.nj.gov/drbc/library/documents/watercode.pdf.
    \44\ A map showing the Delaware River watershed and the 
specified zones is available in the docket (Docket ID No. EPA-HQ-OW-
2023-0222) as well as in each of the support documents associated 
with this rule: Technical Support Document for the Proposed Rule: 
Water Quality Standards to Protect Aquatic Life in the Delaware 
River; Economic Analysis for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River; and 
Environmental Justice Analysis for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River.
    \45\ Delaware River Basin Commission. (2015). ``Existing Use 
Evaluation for Zones 3, 4, & 5 of the Delaware Estuary Based on 
Spawning and Rearing of Resident and Anadromous Fishes.'' September 
30, 2015. https://www.state.nj.us/drbc/library/documents/ExistingUseRpt_zones3-5_sept2015.pdf.
    \46\ Anadromous fish are species that are born and reared as 
juveniles in freshwater, migrate to marine waters where they spend 
most of their adult lives, and return to their natal, freshwater 
rivers to spawn.
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1. Delaware's, New Jersey's, and Pennsylvania's Current Aquatic Life 
Designated Uses
    As described in section III.C. of this preamble, Delaware, New 
Jersey, and Pennsylvania each has its own WQS for the specified zones 
of the Delaware River under its jurisdiction. Delaware's current 
aquatic life designated use for the specified zones of the Delaware 
River includes all life stages, thus including the propagation 
component of the CWA section 101(a)(2) use. New Jersey's aquatic life 
designated use for the specified zones of the Delaware River 
incorporate by reference the designated uses in DRBC's Water Quality 
Regulations. Pennsylvania's aquatic life designated uses for the 
specified zones of the Delaware River align with DRBC's ``maintenance'' 
and ``passage'' designated use (Table 2 of this preamble). Therefore, 
neither New Jersey's nor Pennsylvania's aquatic life designated use for 
the specified zones of the Delaware River include the propagation 
component of the CWA section 101(a)(2) use.

  Table 2--Current Aquatic Life Designated Uses in Zone 3, Zone 4, and
                   Upper-Zone 5 of the Delaware River
------------------------------------------------------------------------
             Entity                           Designated use
------------------------------------------------------------------------
DRBC \1\........................  Maintenance of resident fish and other
                                   aquatic life, passage of anadromous
                                   fish, wildlife.
Delaware \2\....................  Fish, Aquatic Life & Wildlife.\3\
New Jersey \4\..................  The designated uses for the mainstem
                                   Delaware River and Delaware Bay are
                                   those contained in the DRBC Water
                                   Quality Regulations.
Pennsylvania \5\................  Warm Water Fishes (Maintenance Only);
                                   Migratory fishes (Passage Only).\6\
------------------------------------------------------------------------
\1\ Delaware River Basin Commission. ``Administrative Manual--Part III
  Water Quality Regulations with Amendments Through December 7, 2022.''
  Accessed May 3, 2023. https://www.nj.gov/drbc/library/documents/WQregs.pdf.
\2\ Delaware Administrative Code. ``7401 Surface Water Quality
  Standards.'' Title 7 Natural Resources & Environmental Control.
  Delaware Department of Natural Resource and Environmental Control.
  Accessed May 3, 2023. https://regulations.delaware.gov/AdminCode/title7/7000/7400/7401.pdf.
\3\ Delaware defines Fish, Aquatic Life & Wildlife as, ``all animal and
  plant life found in Delaware, either indigenous or migratory,
  regardless of life stage or economic importance.'' A footnote
  specifies that this use includes shellfish propagation.
\4\ New Jersey Administrative Code. ``N. J. A. C. 7:9B Surface Water
  Quality Standards.'' Accessed May 3, 2023. https://dep.nj.gov/wp-content/uploads/rules/rules/njac7_9b.pdf.
\5\ Pennsylvania Code. ``Chapter 93. Water Quality Standards.''
  Commonwealth of Pennsylvania. Accessed May 3, 2023. https://www.pacodeandbulletin.gov/secure/pacode/data/025/chapter93/025_0093.pdf.
\6\ Pennsylvania defines its ``Warm Water Fishes'' designated use as,
  ``Maintenance and propagation of fish species and additional flora and
  fauna which are indigenous to a warm water habitat'' and defines its
  ``Migratory Fishes'' designated use as, ``Passage, maintenance and
  propagation of anadromous and catadromous fishes and other fishes
  which move to or from flowing waters to complete their life cycle in
  other waters.'' For the specified zones of the Delaware River,
  Pennsylvania excluded propagation from the designated uses by
  specifying ``Maintenance Only'' and ``Passage Only'' in parentheses.

2. Delaware's, New Jersey's, and Pennsylvania's Current Dissolved 
Oxygen Criteria
    For dissolved oxygen in the relevant zones, all three states 
incorporate DRBC's water quality criteria by reference; therefore, 
DRBC's dissolved oxygen criteria are the applicable criteria for the 
relevant zones in each state (Table 3 of this preamble). As explained 
above with respect to the aquatic life designated use, DRBC's dissolved 
oxygen criteria for the specified zones of the Delaware River do not 
protect for aquatic life propagation and are therefore not consistent 
with CWA section 101(a)(2) goals.

Table 3--Current Dissolved Oxygen Criteria in Zone 3, Zone 4, and Upper-
                      Zone 5 of the Delaware River
------------------------------------------------------------------------
             Entity               Dissolved oxygen aquatic life criteria
------------------------------------------------------------------------
DRBC \1\........................  24-hour average concentration shall
                                   not be less than 3.5 mg/l. During the
                                   periods from April 1 to June 15, and
                                   September 16 to December 31, the
                                   dissolved oxygen shall not have a
                                   seasonal average less than 6.5 mg/l
                                   in the entire zone.
Delaware \2\....................  For waters of the Delaware River and
                                   Delaware Bay, duly adopted Delaware
                                   River Basin Commission (DRBC) Water
                                   Quality Regulations shall be the
                                   applicable criteria.
New Jersey \3\..................  For parameters with criteria in the
                                   DRBC Water Quality Regulations, the
                                   criteria contained therein are the
                                   applicable criteria.
Pennsylvania \4\................  See DRBC Water Quality Regulations.
------------------------------------------------------------------------
\1\ Delaware River Basin Commission. ``Administrative Manual--Part III
  Water Quality Regulations with Amendments Through December 7, 2022.''
  Accessed May 3, 2023. https://www.nj.gov/drbc/library/documents/WQregs.pdf.
\2\ Delaware Administrative Code. ``7401 Surface Water Quality
  Standards.'' Title 7 Natural Resources & Environmental Control.
  Delaware Department of Natural Resource and Environmental Control.
  Accessed May 3, 2023. https://regulations.delaware.gov/AdminCode/title7/7000/7400/7401.pdf.
\3\ New Jersey Administrative Code. ``N. J. A. C. 7:9B Surface Water
  Quality Standards.'' Accessed May 3, 2023. https://dep.nj.gov/wp-content/uploads/rules/rules/njac7_9b.pdf.
\4\ Pennsylvania Code. ``Chapter 93. Water Quality Standards.''
  Commonwealth of Pennsylvania. Accessed May 3, 2023. https://www.pacodeandbulletin.gov/secure/pacode/data/025/chapter93/025_0093.pdf.


[[Page 88321]]

3. Intersection of Delaware's, New Jersey's, and Pennsylvania's Current 
Aquatic Life Designated Uses and Dissolved Oxygen Criteria With CWA 
101(a)(2) Goals
    Table 4 of this preamble provides a summary outlining whether 
Delaware's, New Jersey's, and Pennsylvania's current aquatic life 
designated uses align with CWA section 101(a)(2) goals and whether each 
state's current dissolved oxygen criteria are protective of an aquatic 
life designated use that includes propagation. As explained above, 
Delaware is the only state that includes aquatic life propagation in 
its designated uses for the specified zones of the Delaware River. 
However, none of the three states' dissolved oxygen water quality 
criteria for the specified zones are protective of fish and shellfish 
propagation. Therefore, none of the states, and by extension none of 
the specified zones of the Delaware River, currently has a set of WQS 
for aquatic life that are fully consistent with the CWA section 
101(a)(2) goals (i.e., ``water quality which provides for the 
protection and propagation of fish, shellfish, and wildlife [. . .]'').

 Table 4--Intersection of Delaware's, New Jersey's, and Pennsylvania's Current Aquatic Life Designated Uses and
                               Dissolved Oxygen Criteria With CWA 101(a)(2) Goals
----------------------------------------------------------------------------------------------------------------
                                                                                             Dissolved oxygen
                                                                Designated use includes   criteria protective of
                State                     Applicable zone(s)     CWA section 101(a)(2)         aquatic life
                                                                 propagation component         propagation
----------------------------------------------------------------------------------------------------------------
Delaware.............................  Upper-5................  Yes....................  No.
New Jersey...........................  3, 4, Upper-5..........  No.....................  No.
Pennsylvania.........................  3, 4...................  No.....................  No.
----------------------------------------------------------------------------------------------------------------

E. Summary of the EPA's Administrator's Determination

    On December 1, 2022, the EPA determined that the CWA section 
101(a)(2) use of propagation is now attainable and therefore revised 
WQS are necessary to protect aquatic life in certain water quality 
management zones of the Delaware River.\47\ Specifically, the EPA 
issued an Administrator's Determination, pursuant to CWA section 
303(c)(4)(B), finding that a revised designated use to protect aquatic 
life propagation and corresponding dissolved oxygen criteria to protect 
that use are necessary in Zone 3, Zone 4, and the upper portion of Zone 
5 (in total, river miles 108.4 to 70.0) of the Delaware River. The 
Administrator's Determination can be accessed at https://www.epa.gov/wqs-tech/federally-promulgated-water-quality-standards-specific-states-territories-and-tribes.
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    \47\ December 1, 2022. Letter from Radhika Fox, Assistant 
Administrator, EPA Office of Water, to Steven J. Tambini, Executive 
Director, Delaware River Basin Commission; Shawn M. Garvin, 
Secretary, Delaware Department of Natural Resources and 
Environmental Control; Shawn M. LaTourette, Commissioner, New Jersey 
Department of Environmental Protection; and Ramez Ziadeh, Acting 
Secretary, Pennsylvania Department of Environmental Protection.
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IV. Proposed Water Quality Standards

A. Scope of EPA's Proposed Rule

    In accordance with the Administrator's Determination, the EPA's 
proposed rule, if finalized, would apply to Zone 3, Zone 4, and the 
upper portion of Zone 5 of the Delaware River (in total, river miles 
108.4 to 70.0), for the states of Delaware, New Jersey, and 
Pennsylvania (Table 5 of this preamble).

 Table 5--Zones of the Delaware River Covered by the EPA's Proposed Rule
------------------------------------------------------------------------
  Segment of the Delaware River       River miles       States affected
------------------------------------------------------------------------
Zone 3..........................  108.4 to 95.0.....  New Jersey,
                                                       Pennsylvania.
Zone 4..........................  95.0 to 78.8......  New Jersey,
                                                       Pennsylvania.
Zone 5--Upper Portion...........  78.8 to 70.0......  Delaware, New
                                                       Jersey.
------------------------------------------------------------------------

B. Proposed Aquatic Life Designated Use

    The EPA is proposing to promulgate a revised aquatic life 
designated use for the specified zones of the Delaware River to meet 
the CWA section 101(a)(2) goals (i.e., ``water quality which provides 
for the protection and propagation of fish, shellfish, and wildlife''), 
as specified in the EPA's Administrator's Determination.\48\ Although 
the relevant zones of the Delaware River are each under the 
jurisdiction of two or more states (Table 5 of this preamble), CWA 
section 303(c) assigns the individual states the role of adopting WQS. 
Therefore, the EPA is evaluating the aquatic life uses on a state-by-
state basis.
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    \48\ The EPA's Administrator's Determination stated, ``EPA is 
determining [. . . that] revised aquatic life designated uses that 
provide for propagation of fish, consistent with CWA section 
101(a)(2) and 40 CFR 131.20(a) [. . .] are necessary for zone 3, 
zone 4, and the upper portion of zone 5 (in total, river miles 108.4 
to 70.0) of the Delaware River Estuary, to meet the requirements of 
the CWA.''
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    As explained in section III.D. of this preamble, Delaware's ``Fish, 
Aquatic Life & Wildlife'' designated use includes all life stages of 
indigenous and migratory organisms; therefore, Delaware's aquatic life 
designated use in the specified zones under its jurisdiction is already 
consistent with the CWA section 101(a)(2) goals and no revisions to 
Delaware's aquatic life designated use are necessary to meet CWA 
requirements. In contrast, New Jersey's and Pennsylvania's aquatic life 
designated uses for the relevant zones of the Delaware River under 
their jurisdiction do not include ``propagation'' and are therefore not 
consistent with CWA section 101(a)(2) goals. As explained in section 
III.E. of this preamble, the EPA determined that propagation is now an 
attainable use in the specified zones of the Delaware River.\49\ 
Therefore, for the portions of the specified zones under New Jersey's 
and Pennsylvania's jurisdiction, a

[[Page 88322]]

revised aquatic life designated use that includes propagation is 
necessary to meet CWA requirements and ensure that the specified zones 
of the Delaware River are consistent with CWA section 101(a)(2) goals.
---------------------------------------------------------------------------

    \49\ December 1, 2022. Letter from Radhika Fox, Assistant 
Administrator, EPA Office of Water, to Steven J. Tambini, Executive 
Director, Delaware River Basin Commission; Shawn M. Garvin, 
Secretary, Delaware Department of Natural Resources and 
Environmental Control; Shawn M. LaTourette, Commissioner, New Jersey 
Department of Environmental Protection; and Ramez Ziadeh, Acting 
Secretary, Pennsylvania Department of Environmental Protection.
---------------------------------------------------------------------------

    Thus, the EPA is proposing to promulgate an aquatic life designated 
use for Zone 3, Zone 4, and the upper portion of Zone 5 of the Delaware 
River (in total, river miles 108.4 to 70.0) for the states of New 
Jersey and Pennsylvania, as follows: Protection and propagation of 
resident and migratory aquatic life.

C. Dissolved Oxygen Criteria To Protect Aquatic Life Propagation

    The EPA is proposing to establish dissolved oxygen criteria--
derived from the latest sound scientific information--for Delaware, New 
Jersey, and Pennsylvania, for the specified zones of the Delaware 
River. The proposed dissolved oxygen criteria would protect the EPA's 
proposed designated use for New Jersey and Pennsylvania, as well as 
Delaware's current aquatic life designated use for the specified zones.
1. Derivation of Dissolved Oxygen Criteria
    To derive protective dissolved oxygen criteria for the specified 
zones of the Delaware River, the EPA used methods adapted from peer-
reviewed literature and data from laboratory studies relevant to 
oxygen-sensitive sturgeon species in the Delaware River. Although the 
methods and data are from peer-reviewed scientific literature, the EPA 
is nonetheless in the process of completing an external peer review on 
the application of these methods and data in this context where the EPA 
is proposing criteria to protect proposed and applicable aquatic life 
designated uses that include propagation. This section presents a 
summary of the data and methods that the EPA used to derive protective 
dissolved oxygen criteria for this proposed rulemaking. First, the EPA 
describes the Agency's existing dissolved oxygen national 
recommendations and guidance documents. Then, the EPA explains how the 
Agency selected three seasons to derive criteria protective of oxygen-
sensitive species in the relevant zones of the Delaware River. Next, 
the EPA details an Atlantic Sturgeon cohort model used to derive 
criteria protective of juvenile Atlantic Sturgeon during the season 
associated with their growth and development. After that, the EPA 
explains how criteria were developed to protect oxygen-sensitive 
species during the other two seasons. Lastly, the EPA concludes with an 
explanation for proposing criteria expressed as percent oxygen 
saturation, rather than as concentration. This section is intended to 
be a high-level summary of the EPA's criteria derivation methods and 
results for this proposed rulemaking. More details and information are 
available in the associated technical support document, Technical 
Support Document for the Proposed Rule: Water Quality Standards to 
Protect Aquatic Life in the Delaware River. The EPA will consider 
information received during the public comment period (detailed above), 
in addition to the external peer review of the technical support 
document, and accordingly may make changes to the proposed criteria for 
a final rule.
Existing the EPA Methodology and Guidance Documents
    Under CWA section 304(a), the EPA publishes, from time to time, 
national recommended aquatic life criteria for a variety of pollutants 
and parameters. The EPA's national recommended criteria for dissolved 
oxygen in freshwater and saltwater environments are from the 1986 
Quality Criteria for Water (``Gold Book'') \50\ and the 2000 Ambient 
Aquatic Life Water Quality Criteria for Dissolved Oxygen (Saltwater): 
Cape Cod to Cape Hatteras (``Virginian Province Document''),\51\ 
respectively. The EPA's recommendations in the Virginian Province 
Document state that, ``in cases where a threatened or endangered 
species occurs at a site, and sufficient data exist to suggest that it 
is more sensitive at concentrations above the criteria, it is 
appropriate to consider development of site-specific criteria based on 
this species.'' \52\ As explained previously in section III.B. of this 
preamble, Atlantic Sturgeon and Shortnose Sturgeon are federally listed 
as endangered under the ESA and are uniquely sensitive to hypoxia. 
Given the availability of laboratory data specific to the oxygen 
requirements of Atlantic Sturgeon and Shortnose Sturgeon, the EPA chose 
to derive site-specific criteria to protect the oxygen-sensitive 
endangered species in the specified zones of the Delaware River and not 
rely on the national recommendations in the Gold Book or Virginian 
Province Document in this instance.
---------------------------------------------------------------------------

    \50\ United States Environmental Protection Agency. (1986). 
Quality Criteria for Water 1986. Document ID: EPA 440/5-86-001. May 
1, 1986. https://www.epa.gov/sites/default/files/2018-10/documents/quality-criteria-water-1986.pdf.
    \51\ United States Environmental Protection Agency. (2000). 
Ambient Aquatic Life Water Quality Criteria for Dissolved Oxygen 
(Saltwater): Cape Cod to Cape Hatteras. Document ID: EPA-822-R-00-
012. November 2000. https://www.epa.gov/sites/default/files/2018-10/documents/ambient-al-wqc-dissolved-oxygen-cape-code.pdf.
    \52\ Id. Page 41.
---------------------------------------------------------------------------

Delineating Seasons for Criteria Derivation
    In consideration of available information, including information 
developed by DRBC, the EPA is proposing to delineate three distinct 
seasons for dissolved oxygen criteria development that are intended to 
protect Atlantic Sturgeon early life stages, while also protecting a 
range of other aquatic species' sensitive life stages in the specified 
zones. The EPA is proposing to define the Spawning and Larval 
Development season as occurring from March 1 to June 30, which 
generally covers spawning and egg and larval development periods for 
many oxygen-sensitive species, including Atlantic Sturgeon, Shortnose 
Sturgeon, American Shad, Atlantic Rock Crab, Channel Catfish, Striped 
Bass, Largemouth Bass, White Perch, and Yellow Perch.\53\ The EPA is 
proposing to define the Juvenile Development season as occurring from 
July 1 to October 31 and the Overwintering season as occurring from 
November 1 to February 28/29, based on young-of-the-year juvenile 
Atlantic Sturgeon growth rates.\54\ By November, growth rates are 
reduced by low water temperatures despite relatively high levels of 
dissolved oxygen.\55\ While the EPA is proposing to define seasons 
largely based on the early life stages of Atlantic Sturgeon, the 
proposed seasons also generally correspond with early life stages of 
other oxygen-sensitive species in the specified zones of the Delaware 
River. By developing criteria that are protective of Atlantic Sturgeon, 
which, as described in section III.B. of this preamble, is the most 
oxygen-sensitive species in the relevant zones of the Delaware River, 
the EPA concluded that the criteria would also be protective of other 
less oxygen-sensitive resident and

[[Page 88323]]

migratory aquatic species in the specified zones of the Delaware River.
---------------------------------------------------------------------------

    \53\ Stoklosa et al. (2018); Delaware River Basin Commission 
(2015); Moberg, T. and M. DeLucia. (2016). Potential Impacts of 
Dissolved Oxygen, Salinity and Flow on the Successful Recruitment of 
Atlantic Sturgeon in the Delaware River. The Nature Conservancy. 
Harrisburg, PA. https://www.conservationgateway.org/ConservationPractices/Freshwater/HabitatProtectionandRestoration/Documents/DelawareAtlanticSturgeonReport_TNC5172016.pdf.
    \54\ Moberg and DeLucia. (2016).
    \55\ This conclusion was based on results of the growth model, 
described in sections 3.3.3 and 4.1.2 of the associated document, 
Technical Support Document for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River.
---------------------------------------------------------------------------

Ecological Modeling To Derive Criteria for the Juvenile Development 
Season
    The EPA obtained recent and high-quality data from a variety of 
sources, described below and detailed in the associated technical 
support document, to evaluate oxygen requirements of Atlantic Sturgeon 
in each season. The EPA quantified water quality conditions in the 
specified zones of the Delaware River using recent and high-quality 
monitoring data from two locations in the Delaware River. Since the 
Atlantic Sturgeon was listed as an endangered species in 2012, there 
have been few recent studies documenting their oxygen requirements. 
However, available data on sturgeon growth and mortality from Campbell 
and Goodman (2004), Niklitschek and Secor (2009a), and EPA (2003), 
along with methods from Niklitschek and Secor (2005) and Niklitschek 
and Secor (2009b), water quality monitoring data, and juvenile Atlantic 
Sturgeon abundance data from the Delaware Department of Natural 
Resources and Environmental Control (DNREC) provided the EPA with 
sufficient data to establish quantitative relationships between age-0 
juvenile sturgeon growth, mortality, and habitat suitability.\56\
---------------------------------------------------------------------------

    \56\ Campbell, J., and L. Goodman. (2004). Acute sensitivity of 
juvenile shortnose sturgeon to low dissolved oxygen concentrations. 
Transactions of the American Fisheries Society 133:722-776; 
Niklitschek, E., and D. Secor. (2009a). Dissolved oxygen, 
temperature and salinity effects on the ecophysiology and survival 
of juvenile Atlantic sturgeon in estuarine waters: I. Laboratory 
results. Journal of Experimental Marine Biology and Ecology 
381:S150-S160. https://doi.org/10.1016/j.jembe.2009.07.018; United 
States Environmental Protection Agency. (2003). Ambient Water 
Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll 
a for the Chesapeake Bay and its Tidal Tributaries. Document ID: EPA 
903-R-03-002. April 2003. https://nepis.epa.gov/Exe/ZyPDF.cgi/P100YKPQ.PDF?Dockey=P100YKPQ.PDF; Niklitschek, E.J., and D.H. Secor. 
(2005). Modeling spatial and temporal variation of suitable nursery 
habitats for Atlantic sturgeon in the Chesapeake Bay. Estuarine, 
Coastal and Shelf Science 64:135-148. https://doi.org/10.1016/j.ecss.2005.02.012; Niklitschek, E.J., and D.H. Secor. (2009b). 
Dissolved oxygen, temperature and salinity effects on the 
ecophysiology and survival of juvenile Atlantic sturgeon in 
estuarine waters: II. Model development and testing. Journal of 
Experimental Marine Biology and Ecology 381:S161-S172. https://doi.org/10.1016/j.jembe.2009.07.019; USGS 01467200 Delaware River at 
Penn's Landing, Philadelphia, PA. Retrieved March 9, 2023. https://waterdata.usgs.gov/nwis/inventory/?site_no=01467200&agency_cd=USGS; 
USGS 01477050 Delaware River at Chester PA. Retrieved January 31, 
2023. https://waterdata.usgs.gov/nwis/inventory?agency_code=USGS&site_no=01477050; Park, I. (2023). State 
of Delaware Annual Compliance Report for Atlantic Sturgeon. Delaware 
Division of Fish and Wildlife, Department of Natural Resources and 
Environmental Control. September 2023.
---------------------------------------------------------------------------

    The EPA followed the peer-reviewed cohort modeling approach of 
Niklitschek and Secor (2005) to evaluate the effects of temperature, 
salinity, and dissolved oxygen on the potential growth and mortality of 
a hypothetical cohort or group of juvenile Atlantic Sturgeon spawned 
during a single year.\57\ The cohort model uses growth and mortality 
rates to calculate the instantaneous daily production potential, or the 
instantaneous amount of biomass produced per unit of cohort biomass per 
day. The EPA used the cohort model to estimate the fraction of the 
cohort that survives from July 1 through October 31 (i.e., the Juvenile 
Development season) and the relative change in biomass for the same 
period.
---------------------------------------------------------------------------

    \57\ Water temperature and salinity can affect the oxygen 
requirements of aquatic species and are needed to compute percent 
oxygen saturation, a measure of dissolved oxygen availability to 
aquatic organisms, from dissolved oxygen concentrations.
---------------------------------------------------------------------------

    As part of the cohort model, the EPA developed a new mortality 
model and implemented a peer-reviewed bioenergetics-based growth model 
described by Niklitschek and Secor (2009b) to predict the daily 
instantaneous mortality rate and growth rate, respectively, for members 
of the cohort. To develop a mortality model, the EPA fit a regression 
to experimental data to predict mortality resulting from low dissolved 
oxygen at any given temperature and percent oxygen saturation.\58\ 
Mortality rates of juvenile sturgeons increased with declining 
dissolved oxygen levels and increased at higher rates with both 
declining dissolved oxygen and increasing water temperature. The EPA 
validated the results of the mortality model by using observed water 
quality data to predict relative abundance of the Atlantic Sturgeon 
young-of-year cohort on October 31 and comparing those results to catch 
data from DNREC's juvenile abundance surveys.\59\ The growth model 
takes a bioenergetic approach that accounts for temperature-controlled 
maximum metabolic rates that may be further limited by oxygen levels. 
Low oxygen levels limit overall metabolic rates and cause a shift in 
the allocation of available energy away from growth. Predicted growth 
rates reflect the balance between energy inputs and losses and are 
therefore reduced by low oxygen. Water quality monitoring data in the 
relevant zones of the Delaware River show that the lowest oxygen levels 
coincided with the highest water temperatures, resulting in lower 
growth rates than either condition would cause alone.
---------------------------------------------------------------------------

    \58\ Experimental data are from Campbell and Goodman 2004, 
Niklitschek and Secor 2009a.
    \59\ USGS 01467200 Delaware River at Penn's Landing, 
Philadelphia, PA. Retrieved March 9, 2023. https://waterdata.usgs.gov/nwis/inventory/?site_no=01467200&agency_cd=USGS; 
USGS 01477050 Delaware River at Chester, PA. Retrieved January 31, 
2023. https://waterdata.usgs.gov/nwis/inventory?agency_code=USGS&site_no=01477050; Park (2023).
---------------------------------------------------------------------------

    Habitat Suitability Indices have been used in the context of fish-
habitat relationships, conservation management, and habitat evaluation 
to quantify the capacity of a given habitat to support essential life 
functions (e.g., growth, survival, reproduction) of a selected 
species.\60\ For this proposed rulemaking, the EPA defined a Habitat 
Suitability Index (HSI) for Atlantic Sturgeon as the instantaneous 
daily production potential, which was calculated using the cohort 
model. HSI evaluates the combined effect of percent oxygen saturation, 
water temperature, and salinity on the potential growth and survival of 
juvenile Atlantic Sturgeon during the Juvenile Development season. The 
EPA used quantile generalized additive models (QGAMs) to quantify 
relationships between computed values of HSI in each year and 
corresponding seasonal percentiles of daily dissolved oxygen for that 
year.\61\ QGAMs can model the non-linear relationship between dissolved 
oxygen and HSI as well as predict the expected median HSI, rather than 
the expected mean.
---------------------------------------------------------------------------

    \60\ E.g., Woodland, R.J., Secor, D.H., and Niklitschek, E.J. 
(2009). Past and Future Habitat Suitability for the Hudson River 
Population of Shortnose Sturgeon: A Bioenergetic Approach to 
Modeling Habitat Suitability for an Endangered Species. American 
Fisheries Society Symposium 69: 589-604; Collier, J.J., Chiotti, 
J.A., Boase, J., Mayer, C.M., Vandergoot, C.S., and Bossenbroek, 
J.M. (2022). Assessing habitat for lake sturgeon (Acipenser 
fulvescens) reintroduction to the Maumee River, Ohio using habitat 
suitability index models. Journal of Great Lakes Research. 48(1): 
219-228. https://doi.org/10.1016/j.jglr.2021.11.006; Brown, S.K., 
Buja, K.R., Jury, S.H., Monaco, M.E., and Banner, A. (2000). Habitat 
Suitability Index Models for Eight Fish and Invertebrate Species in 
Casco and Sheepscot Bays, Maine. North American Journal of Fisheries 
Management, 20(2): 408-435, https://doi.org/10.1577/1548-8675(2000)020%3C0408:HSIMFE%3E2.3.CO;2.
    \61\ A percentile (e.g., 10th percentile) is the dissolved 
oxygen level below which the corresponding fraction (e.g., 10%) of 
the daily dissolved oxygen values during the season falls below. In 
this case, the season is the Juvenile Development season (July 1-
October 31).
---------------------------------------------------------------------------

    The EPA followed the approach of Niklitschek and Secor (2005) to 
define suitable habitat for juvenile Atlantic Sturgeon growth and 
survival as habitats with water quality resulting in HSI greater than 
zero. When HSI is less than or equal to zero, seasonal average 
mortality rates are greater than or equal to seasonal average growth 
rates and the overall biomass of the cohort is likely to decrease. 
Conversely, a cohort of

[[Page 88324]]

juveniles utilizing habitat with HSI greater than zero has the 
potential to increase its biomass during the Juvenile Development 
season, thus contributing to successful propagation. Therefore, to 
derive protective dissolved oxygen criteria, the EPA evaluated seasonal 
percentiles of percent oxygen saturation to find the lowest value at 
which the QGAMs predict expected median HSI>0 as the minimum thresholds 
for percent oxygen saturation that, if attained, would provide suitable 
habitat during that seasonal period. The EPA requests comment on the 
conclusion that HSI greater than zero defines suitable habitat for 
juvenile Atlantic Sturgeon growth and survival, or alternatively, if 
evidence could support that a value of HSI less than zero could also be 
protective or if a higher HSI threshold may be needed to protect 
propagation in the specified zones. Similarly, the EPA requests comment 
on its use of QGAM to relate percentiles of dissolved oxygen levels to 
the conditional median HSI. These models can be understood to find the 
minimum dissolved oxygen level that if achieved would result in an 
expectation that HSI would be equal to or greater than zero as often or 
more often than if it is less than zero. As an alternative, the QGAM 
could predict a lower conditional percentile, providing a high degree 
of certainty that HSI would be greater than zero if the dissolved 
oxygen level was attained. For example, at the dissolved oxygen level 
where the expected 25th percentile HSI=0, HSI would be expected to 
equal or exceed zero 75% of the time.
    The predicted HSI value relies on an expected distribution of 
percent oxygen saturation values during the season; therefore, the EPA 
selected two percent oxygen saturation percentiles as thresholds at or 
above which median HSI is expected to be greater than zero to maintain 
the expected distribution of percent oxygen saturation values. These 
two percentiles--the 10th percentile and the 50th percentile--describe 
the protective seasonal distribution of dissolved oxygen values. When 
both the 10th percentile and 50th percentile are attained, they 
function together to ensure that a detrimental shift in the oxygen 
distribution (i.e., a shift causing more low oxygen levels) at either 
the low end (10th percentile) or the center (50th percentile) of the 
dissolved oxygen distribution has not occurred. Median HSI is expected 
to be zero or higher, allowing the annual cohort of juvenile Atlantic 
Sturgeon to maintain or increase its biomass, when the 10th percentile 
of oxygen saturation is at least 66% and the 50th percentile, or 
median, of oxygen saturation is at least 74%. Therefore, the EPA 
expects oxygen levels will not impair juvenile Atlantic Sturgeon during 
the Juvenile Development season if the 10th percentile of oxygen 
saturation is at least 66% and the 50th percentile of oxygen saturation 
is at least 74%.
Criteria Development for Spawning and Larval Development and 
Overwintering Seasons
    The Atlantic Sturgeon cohort model described above relies on 
experimental studies that were conducted using juvenile Atlantic 
Sturgeon and therefore provide information that is most relevant to 
juvenile growth and survival.\62\ Additionally, the underlying studies 
allocated most experimental treatments to water temperatures between 12 
[deg]C and 28 [deg]C, with only a single experimental treatment at 6 
[deg]C and none at lower water temperatures.\63\ The EPA's cohort 
modeling approach therefore does not apply to spawning and larval 
development lifestages and has minimal relevance to the overwintering 
period. Accordingly, the EPA did not use the cohort model to derive 
criteria for the Spawning and Larval Development or the Overwintering 
seasons.
---------------------------------------------------------------------------

    \62\ Experimental data are from Campbell and Goodman 2004 and 
Niklitschek and Secor 2009a.
    \63\ Niklitschek and Secor 2009a.
---------------------------------------------------------------------------

    Instead, the EPA concluded that Atlantic Sturgeon larvae were 
likely to be as sensitive to low dissolved oxygen as juvenile Atlantic 
Sturgeon \64\ and that overwintering juveniles have temperature-limited 
metabolism and therefore have similar or slightly lower oxygen 
requirements than juveniles in warmer waters (e.g., summer water 
temperatures).\65\ Thus, the EPA determined that the percent oxygen 
saturation threshold that would be protective of juveniles experiencing 
stressful (high) water temperatures during the Juvenile Development 
season would also be protective of larvae and overwintering juveniles 
not experiencing high water temperatures. Therefore, the EPA expects 
oxygen levels will not impair Atlantic Sturgeon when the 10th 
percentile of oxygen saturation is at least 66% during the Spawning and 
Larval Development and Overwintering seasons. The EPA notes that from 
2002-2022, the median oxygen level during the Spawning and Larval 
Development and Overwintering seasons was well above levels expected to 
negatively impact either Atlantic Sturgeon or other oxygen-sensitive 
species. Therefore, the EPA concluded that a second criterion for a 
50th percentile was not needed during these seasons.
---------------------------------------------------------------------------

    \64\ Stoklosa et al. (2018); United States Environmental 
Protection Agency. (2000). Ambient Aquatic Life Water Quality 
Criteria for Dissolved Oxygen (Saltwater): Cape Cod to Cape 
Hatteras. Document ID: EPA-822-R-00-012. November 2000. https://www.epa.gov/sites/default/files/2018-10/documents/ambient-al-wqc-dissolved-oxygen-cape-code.pdf.
    \65\ Niklitschek and Secor (2009a, 2009b).
---------------------------------------------------------------------------

Criteria Expressed as Percent Oxygen Saturation
    Finally, the EPA derived the proposed criteria in terms of percent 
oxygen saturation, rather than in units of concentration (such as 
milligrams per liter or mg/L) for two main reasons.\66\ First, 
physiological effects of oxygen on aquatic organisms are directly 
related to percent oxygen saturation and indirectly related to 
dissolved oxygen concentration. As noted by Niklitschek and Secor 
(2009a), percent oxygen saturation or partial pressure are the most 
biologically relevant measures of oxygen because they determine the 
maximum rate at which aquatic organisms may obtain oxygen from the 
water. Second, percent oxygen saturation varies with water temperature 
less than dissolved oxygen concentration. Because oxygen solubility is 
higher in cold water than warm water, dissolved oxygen concentrations 
are often much higher in cold water. The strong negative relationship 
between dissolved oxygen concentration and temperature can complicate 
the interpretation of seasonal dissolved oxygen patterns. For example, 
in the Delaware River, dissolved oxygen concentrations increase quickly 
during fall as temperatures decrease, even though percent saturation 
increases more slowly. In this example, the increasing oxygen 
concentration gives the appearance that oxygen availability to aquatic 
organisms is increasing more rapidly than it is actually increasing. 
For Atlantic Sturgeon, this means that low levels of percent oxygen 
saturation may continue to impact growth and survival even though 
dissolved oxygen concentrations increase. Given this relationship 
between temperature and dissolved oxygen concentration, criteria 
expressed as concentration will be above or below the protective 
threshold at various times of the year as

[[Page 88325]]

temperature changes, whereas criteria expressed as percent oxygen 
saturation can be protective throughout the year.
---------------------------------------------------------------------------

    \66\ Percent oxygen saturation and dissolved oxygen 
concentration are two different ways to measure oxygen levels in 
water. Dissolved oxygen concentration is the amount of oxygen 
dissolved in the water, typically represented as milligrams of 
oxygen per liter of water. Percent oxygen saturation is the ratio, 
expressed as a percentage, of the dissolved oxygen concentration in 
the water to the dissolved oxygen concentration when at equilibrium 
with the atmosphere.
---------------------------------------------------------------------------

2. Proposed Dissolved Oxygen Criteria
    The EPA's proposed dissolved oxygen criteria cover three distinct 
seasons based largely on Atlantic Sturgeon early life stages and are 
intended to protect all oxygen-sensitive species in the Delaware River, 
as explained above. The Spawning and Larval Development season occurs 
between March 1st and June 30th and captures a comprehensive range of 
resident aquatic species' spawning periods.\67\ The Juvenile 
Development season occurs between July 1st and October 31st and 
captures critical early life stage growth and development for young-of-
the-year Atlantic Sturgeon. The Overwintering season occurs between 
November 1st and February 28th (or 29th, in a leap year), when juvenile 
Atlantic Sturgeon growth is limited by low water temperatures.
---------------------------------------------------------------------------

    \67\ Stoklosa et al. (2018); Delaware River Basin Commission 
(2015).
---------------------------------------------------------------------------

    Each season has water quality criteria that each consist of three 
components: magnitude, duration, and exceedance frequency. The 
magnitude component indicates the required level of dissolved oxygen in 
the water, which in this proposal is presented in units of percent 
oxygen saturation. The duration component specifies the time period 
over which water quality is averaged before comparison with the 
criteria magnitude; in this proposal, the duration is a daily 
average.\68\ The exceedance frequency component specifies how often 
(e.g., percentage of the time) each criterion can be exceeded in each 
season while still ensuring that the use is protected. For this 
proposed rulemaking, the exceedance frequency is determined based on 
the dissolved oxygen percentile from which the magnitude is derived 
(i.e., the 10th percentile can be exceeded 10% of the time, which for a 
season consisting of 123 days is 12 cumulative days of exceedance). For 
dissolved oxygen, an exceedance occurs when the oxygen level in the 
water is below the criterion value.
---------------------------------------------------------------------------

    \68\ The EPA selected a daily average duration because it is a 
readily measurable indicator of the oxygen levels at a daily 
timescale. The daily average is protective because variability of 
dissolved oxygen levels on a single day is small in the Delaware 
River.
---------------------------------------------------------------------------

    In this proposed rulemaking, the Spawning and Larval Development 
and Overwintering seasons each have a single, identical dissolved 
oxygen criterion with a magnitude of 66% oxygen saturation, a daily 
average duration, and a 10% exceedance frequency (which allows for up 
to 12 days of cumulative exceedance during each of these two seasons) 
(Table 6 of this preamble). The Juvenile Development season has two 
individually applicable dissolved oxygen criteria that together define 
a protective seasonal distribution of percent oxygen saturation. The 
criteria differ in both magnitude and exceedance frequency and both 
levels must be attained. The first Juvenile Development criterion 
defines the lower end of the distribution of oxygen levels and consists 
of a magnitude of 66% oxygen saturation, a daily average duration, and 
a 10% exceedance frequency (which allows for up to 12 days cumulative 
exceedance during the season). The second Juvenile Development 
criterion defines the center of the distribution and consists of a 
magnitude of 74% oxygen saturation, a daily average duration, and a 50% 
exceedance frequency (which allows for up to 61 days cumulative 
exceedance during the season) (Table 6 of this preamble).

                              Table 6--The EPA's Proposed Dissolved Oxygen Criteria
----------------------------------------------------------------------------------------------------------------
                                             Magnitude
                                             (percent
                 Season                       oxygen               Duration              Exceedance frequency
                                            saturation)
----------------------------------------------------------------------------------------------------------------
Spawning and Larval Development (March 1-             66  Daily verage..............  10% (12 Days Cumulative).
 June 30).
Juvenile Development (July 1-October 31)              66  Daily Average.............  10% (12 Days Cumulative).
                                                      74  Daily Average.............  50% (61 Days Cumulative).
Overwintering (November 1-February 28/                66  Daily Average.............  10% (12 Days Cumulative).
 29).
----------------------------------------------------------------------------------------------------------------

3. Alternative Options Considered
    During the criteria derivation process, the EPA made several 
decisions based on the best available sound scientific information to 
ensure the dissolved oxygen criteria would be protective of the 
applicable and proposed aquatic life designated uses. In this section, 
the EPA presents three alternative options the Agency considered. For 
each alternative, the EPA examined information currently available at 
the time of this proposal. The EPA has concerns about whether each 
alternative would be protective of the aquatic life designated uses 
that include propagation; therefore, the EPA did not include any of 
these alternatives as part of its lead proposed criteria. However, the 
EPA requests comment and additional information on whether and how one 
or more of these alternatives could protect the applicable and proposed 
aquatic life designated uses in the specified zones of the Delaware 
River and if so, what anticipated benefits would be associated with the 
alternative compared to the EPA's proposed criteria.\69\
---------------------------------------------------------------------------

    \69\ More information is available in the associated document, 
Technical Support Document for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River.
---------------------------------------------------------------------------

    Alternative 1: Dissolved Oxygen Criteria Expressed as Concentration 
(mg/L).
    The EPA's proposed dissolved oxygen criteria are expressed as 
percent oxygen saturation, as described in section IV.C.1 of this 
preamble. However, the EPA recognizes that some stakeholders might be 
more familiar with dissolved oxygen criteria expressed as concentration 
or might have other reasons for preferring criteria expressed as 
concentration. The EPA is seeking comment on whether dissolved oxygen 
criteria expressed as concentration (mg/L) would be protective of 
oxygen-sensitive species during each season.
    To calculate Juvenile Development season criteria expressed as 
concentration (mg/L), the EPA followed an analogous approach to the 
method used for determining criteria as percent oxygen saturation, as 
explained in section IV.C.1 of this preamble. The EPA used quantile 
generalized additive models relating seasonal percentiles of dissolved 
oxygen concentration to the expected median habitat suitability index 
(HSI). The EPA selected as the alternative criteria values the 
dissolved

[[Page 88326]]

oxygen concentration for which the expected median HSI is zero (Table 7 
of this preamble).
    To calculate dissolved oxygen criteria expressed as concentration 
for the Spawning and Larval Development and Overwintering seasons, the 
EPA started with the criteria computed as percent oxygen saturation 
(Table 6 of this preamble) and converted each of these to a 
concentration using each of the following two approaches, which 
differed based on water temperature assumptions.\70\ The EPA's first 
approach uses the 90th percentile of water temperatures in each season, 
whereas the second approach uses the average water temperature in each 
season.\71\ The 90th percentile approximates the highest water 
temperature in each season, which corresponds to when dissolved oxygen 
levels are generally at their lowest and therefore impacts to aquatic 
life are most likely to occur. In the Delaware River, the highest 
temperatures in the Spawning and Larval Development season occur in 
late June and the highest temperatures in the Overwintering season 
occur in early November. On the other hand, the EPA's second approach 
using an average water temperature results in the concentration that 
minimizes the magnitude of deviations in either direction from the 
protective level across the season. Because the average water 
temperature is lower than the 90th percentile water temperature, the 
EPA's second approach resulted in higher dissolved oxygen 
concentrations than the first approach (Table 7 of this preamble).
---------------------------------------------------------------------------

    \70\ The EPA assumed salinity = 0 for each conversion from 
percent oxygen saturation to concentration in the Spawning and 
Larval Development and Overwintering seasons.
    \71\ Seasonal 90th percentile and mean water temperature were 
calculated using the daily climatology computed for Chester for 
March 1, 2012-June 30th, 2022, for the Spawning and Larval 
Development season and November 1, 2011-February 28, 2022, for the 
Overwintering season.
---------------------------------------------------------------------------

    In table 7 below, the EPA leads with alternative criteria based on 
the 90th percentile water temperatures because existing dissolved 
oxygen criteria guidance and criteria derivation efforts in other 
states have commonly focused on the warmest conditions that occur, 
which are the most critical for mitigating impacts to aquatic life due 
to low oxygen.\72\ For consideration, the EPA presents alternative 
criteria based on average water temperatures in parentheses.
---------------------------------------------------------------------------

    \72\ United States Environmental Protection Agency. (2000). 
Ambient Aquatic Life Water Quality Criteria for Dissolved Oxygen 
(Saltwater): Cape Cod to Cape Hatteras. Document ID: EPA-822-R-00-
012. November 2000. https://www.epa.gov/sites/default/files/2018-10/documents/ambient-al-wqc-dissolved-oxygen-cape-code.pdf; Batiuk, 
R.A., Breitburg, D.L., Diaz, R.J., Cronin, T.M., Secor, D.H., and 
Thursby, G. (2009). Derivation of habitat-specific dissolved oxygen 
criteria for Chesapeake Bay and its tidal tributaries. Journal of 
Experimental Marine Biology and Ecology 381: S204-S215. https://doi.org/10.1016/j.jembe.2009.07.023.

                  Table 7--Alternative 1: Dissolved Oxygen Criteria Expressed as Concentration
                                                     [mg/L]
----------------------------------------------------------------------------------------------------------------
                                         Water
              Season                  temperature   Magnitude  (mg/        Duration         Exceedance frequency
                                       ([deg]C)           L)
----------------------------------------------------------------------------------------------------------------
Spawning and Larval Development      * 23.3 (14.7)     * 5.6 (6.7)  Daily Average........  10% (12 Days
 (March 1-June 30).                                                                         Cumulative).
Juvenile Development (July 1-              \+\ N/A             5.4  Daily Average........  10% (12 Days
 October 31).                                                                               Cumulative).
N/A \+\...........................             6.1   Daily Average  50% (61 Days
                                                                     Cumulative).
Overwintering (November 1-February    * 12.4 (5.6)     * 7.0 (8.3)  Daily Average........  10% (12 Days
 28/29).                                                                                    Cumulative).
----------------------------------------------------------------------------------------------------------------
* The 90th percentile of seasonal water temperature and corresponding criterion is used for the main estimate,
  while the average water temperature and corresponding criterion is shown in parentheses.
\+\ Water temperature is not applicable during the Juvenile Development season because the criteria magnitudes
  are derived from the EPA's Atlantic Sturgeon cohort model, described in section IV.C.1 of this preamble.

    Concentration-based criteria derived using the EPA's first approach 
(based on the 90th percentile water temperatures) would be equivalent 
to the EPA's proposed 66% oxygen saturation when water temperature is 
near the 90th percentile temperature and oxygen is near the lowest 
point in each season. However, during periods in each season when water 
temperature is lower than the 90th percentile temperature, the 
concentration-based criteria would be below the level that is 
equivalent to the EPA's proposed 66% oxygen saturation level. For 
example, when water temperature is 2 [deg]C in mid-winter, oxygen 
saturation is 66% when the dissolved oxygen concentration is 9.1 mg/L. 
The EPA therefore has concerns about whether dissolved oxygen criteria 
expressed as concentration for this alternative would be protective for 
the Spawning and Larval Development and Overwintering seasons. Similar 
to the first approach, the concentration derived using the EPA's second 
approach (average water temperature) is also below the level that is 
equivalent to 66% oxygen saturation when water temperature is below the 
seasonal average. During periods in each season when the water 
temperature is warmer than the average, concentrations calculated using 
the EPA's second approach would result in an oxygen saturation higher 
than 66%.\73\
---------------------------------------------------------------------------

    \73\ More information on dissolved oxygen trends in the 
specified zones of the Delaware River is available in the associated 
rule documents, Technical Support Document for the Proposed Rule: 
Water Quality Standards to Protect Aquatic Life in the Delaware 
River and Economic Analysis for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River.
---------------------------------------------------------------------------

    The EPA provided the concentrations in table 7 of this preamble 
that result from the methods described above to help facilitate public 
comment. The EPA also requests public input and supporting information 
about other ways the Agency could develop dissolved oxygen criteria 
expressed as concentration--particularly for the Spawning and Larval 
Development and Overwintering seasons--to protect the relevant aquatic 
life uses in accordance with the CWA.
    Alternative 2: Single Dissolved Oxygen Criterion During the 
Juvenile Development Season with a 10% Exceedance Frequency.
    The EPA's proposed dissolved oxygen criteria for the critical 
Juvenile Development season consist of two values--one that may be 
exceeded 10% of the time and one that may be exceeded 50% of the time--
that must both be met during the season, as explained in section IV.C.1 
of this preamble. However, the EPA recognizes that some stakeholders 
might prefer the simpler criteria framework a single criterion would 
afford or may have other reasons for preferring a single value.

[[Page 88327]]

    The EPA is seeking comment and supporting information on applying a 
single dissolved oxygen criterion with a 10% exceedance frequency 
during the Juvenile Development season, including whether criteria 
expressed with a single criterion would protect the applicable and 
proposed aquatic life designated uses. This could mean applying a 
single criterion of 66% oxygen saturation (or 5.4 mg/L, if expressed as 
concentration) with a 10% exceedance frequency for the Juvenile 
Development season. The Overwintering and Spawning and Larval 
Development seasons are unaffected by this alternative.
    The EPA also requests public input and supporting information about 
other potential options the Agency could consider for dissolved oxygen 
criteria in the form of a single criterion to protect the aquatic life 
uses in accordance with the CWA.
    Alternative 3: Inclusion of a 1-in-3-Year Interannual Exceedance 
Frequency.
    The EPA's proposed criteria do not include an interannual 
exceedance frequency and therefore would need to be met every year. 
However, the EPA recognizes that some stakeholders might prefer 
criteria with an interannual exceedance frequency to help accommodate 
the impact of environmental variability on dissolved oxygen conditions 
in the specified zones of the Delaware River. The EPA is seeking 
comment and supporting information on the addition of a 1-in-3-year 
interannual exceedance frequency as part of the dissolved oxygen 
criteria. The EPA is particularly interested in how and why this 
approach would protect the applicable and current aquatic life uses.
    If a 1-in-3-year interannual exceedance frequency were included as 
part of the dissolved oxygen criteria, it would mean that in any three-
year period, all criteria would need to be attained in at least two 
years. An exceedance would occur in any year where one or more of the 
criteria were not attained. The following two examples describe how a 
1-in-3-year interannual exceedance frequency could function.
    Example 1: If, in a given year, the dissolved oxygen during the 
Juvenile Development season fell below 66% saturation more than 10% of 
the time, then that year would not meet the Juvenile Development 10th 
percentile criterion. Therefore, that year would count as one year of 
exceedance towards the 1-in-3-year interannual exceedance frequency. If 
another criterion, for example the Spawning and Larval Development 
criterion, was not met in that same year, then it would still only 
count as one year of exceedance despite the fact that two criteria were 
not met that year (Table 8 of this preamble).

     Table 8--Example 1 Scenario Where Dissolved Oxygen Criteria With the 1-in-3-Year Interannual Exceedance
                                                Frequency Are Met
----------------------------------------------------------------------------------------------------------------
                                                            Was the seasonal criterion met?
                Season                --------------------------------------------------------------------------
                                                Year 1                   Year 2                   Year 3
----------------------------------------------------------------------------------------------------------------
Spawning and Larval Development......  No.....................  Yes....................  Yes.
Juvenile Development--10th Percentile  No.....................  Yes....................  Yes.
Juvenile Development--50th Percentile  Yes....................  Yes....................  Yes.
Overwintering........................  Yes....................  Yes....................  Yes.
Does the Full Year Meet Criteria?....  No.....................  Yes....................  Yes.
----------------------------------------------------------------------------------------------------------------

    Example 2: If, in a given year, the dissolved oxygen during the 
Juvenile Development season fell below 66% saturation more than 10% of 
the time, then that year would not meet the Juvenile Development 10th 
percentile criterion. If the following year, the Juvenile Development 
season fell below 74% saturation more than 50% of the time, then that 
year would not meet the Juvenile Development 50th percentile criterion 
(Table 9 of this preamble). In this scenario, the first and second year 
in the three-year period both did not meet the criteria; therefore, the 
interannual exceedance frequency was not met.

     Table 9--Example 2 Scenario Where Dissolved Oxygen Criteria With the 1-in-3-Year Interannual Exceedance
                                              Frequency Are Not Met
----------------------------------------------------------------------------------------------------------------
                                                            Was the seasonal criterion met?
                Season                --------------------------------------------------------------------------
                                                Year 1                   Year 2                   Year 3
----------------------------------------------------------------------------------------------------------------
Spawning and Larval Development......  Yes....................  Yes....................  Yes.
Juvenile Development--10th Percentile  No.....................  Yes....................  Yes.
Juvenile Development--50th Percentile  Yes....................  No.....................  Yes.
Overwintering........................  Yes....................  Yes....................  Yes.
Does the Full Year Meet Criteria?....  No.....................  No.....................  Yes.
----------------------------------------------------------------------------------------------------------------

    The EPA has historically considered it appropriate to apply a 1-in-
3-year exceedance frequency in the context of aquatic life criteria for 
toxic pollutants, based on the ability of aquatic ecosystems to recover 
from criteria exceedances and natural variations in flow and the 
concentrations of the pollutant in a waterbody.\74\ However, the EPA 
does not typically apply this construct to criteria for conventional 
water quality parameters like dissolved

[[Page 88328]]

oxygen due to inherent differences between these parameters and toxic 
pollutants. For example, dissolved oxygen is typically not directly 
regulated in the same manner as toxic pollutants because low dissolved 
oxygen conditions (such as hypoxia) are a symptom of a related issue, 
such as nutrient or ammonia pollution.\75\ The EPA also requests public 
input and supporting information regarding any scientific approaches 
that can be used to predict the impact of periodic low oxygen levels on 
populations of aquatic organisms.
---------------------------------------------------------------------------

    \74\ Stephen, C.E., Mount, D.I., Hansen, D.J., Gentile, J.R., 
Chapman, G.A., and Brungs, W.A. (1985). Guidelines for Deriving 
Numerical National Water Quality Criteria for the Protection of 
Aquatic Organisms and Their Uses. United States Environmental 
Protection Agency. Document ID: PB85-227049. https://www.epa.gov/sites/default/files/2016-02/documents/guidelines-water-quality-criteria.pdf; United States Environmental Protection Agency. (2023). 
Proceedings from the EPA Frequency and Duration Experts Workshop: 
September 11-12, 2019. Document ID: EPA-820-R-23-002. February 2023. 
https://www.epa.gov/system/files/documents/2023-02/proceedings-frequency-duration-workshop.pdf.
    \75\ United States Environmental Protection Agency. (2000). 
Ambient Aquatic Life Water Quality Criteria for Dissolved Oxygen 
(Saltwater): Cape Cod to Cape Hatteras. Document ID: EPA-822-R-00-
012. November 2000. https://www.epa.gov/sites/default/files/2018-10/documents/ambient-al-wqc-dissolved-oxygen-cape-code.pdf.
---------------------------------------------------------------------------

V. Endangered Species Act Consultation

    Section 7(a)(2) of the Endangered Species Act (ESA) requires that 
each Federal Agency ensure that any action authorized, funded, or 
carried out by such Agency is not likely to jeopardize the continued 
existence of any endangered or threatened species or result in the 
destruction or adverse modification of critical habitat. Pursuant to 
section 7(a)(2) of the ESA, the EPA will consult with NOAA Fisheries 
concerning this rulemaking action proposing a designated aquatic life 
use including propagation and associated dissolved oxygen criteria in 
the specified zones of the Delaware River. The EPA will work closely 
with NOAA Fisheries to ensure that any WQS the Agency finalizes are not 
likely to jeopardize the continued existence of any endangered or 
threatened species or result in the destruction or adverse modification 
of designated critical habitat in the specified zones of the Delaware 
River. As a result of this consultation, the EPA may modify some 
provisions of this proposed rule.

VI. Applicability

    The EPA is proposing a Federal designated use that would apply in 
New Jersey and Pennsylvania, in addition to those states' designated 
uses that are already applicable. This means that for the specified 
zones of the Delaware River, the EPA is proposing to supplement, rather 
than replace, New Jersey's and Pennsylvania's currently applicable 
aquatic life designated uses. Therefore, New Jersey's and 
Pennsylvania's currently applicable aquatic life designated uses would 
remain applicable for CWA purposes. Those states' current water quality 
criteria associated with those uses would also remain applicable for 
CWA purposes, with the exception of any aquatic life criteria for 
dissolved oxygen, which would be replaced by the criteria that the EPA 
promulgates through this rulemaking, if finalized.\76\ The EPA 
concluded that this approach was the best way to make clear which of 
the states' WQS would and would not be revised by this rulemaking, if 
finalized. The EPA requests comment on this approach.
---------------------------------------------------------------------------

    \76\ In the December 1, 2022, Administrator's Determination, the 
EPA determined that revised dissolved oxygen criteria are necessary 
to protect a propagation designated use. This proposed rulemaking 
includes dissolved oxygen criteria that are protective of all life 
stages of resident and migratory aquatic life species in the 
Delaware River (section IV.C. of this preamble).
---------------------------------------------------------------------------

    In addition, the EPA is proposing dissolved oxygen criteria that 
would replace Delaware's, New Jersey's, and Pennsylvania's existing 
dissolved oxygen criteria for the specified zones of the Delaware 
River. The EPA notes that there are aquatic life criteria for 
pollutants and parameters other than dissolved oxygen that are in 
effect for CWA purposes--not only in the zones covered by this proposed 
rulemaking, but also for other zones of the Delaware River that already 
include aquatic life propagation as a designated use; those criteria 
are not impacted by this rulemaking.
    Since the EPA is only proposing to promulgate revised dissolved 
oxygen criteria for the specified zones of the Delaware River, 
Delaware, New Jersey, and Pennsylvania should evaluate whether other 
aquatic life criteria should similarly be added or revised for the 
specified zones or other zones of the Delaware River. One way these 
states can review their WQS is through the triennial review process. As 
explained in section III of this preamble, states must review their WQS 
at least once every three years and, if appropriate, revise standards 
or adopt new standards (40 CFR 131.20(a)). The EPA recommends that 
Delaware, New Jersey, and Pennsylvania review their existing aquatic 
life criteria during their next triennial review to determine if new or 
revised aquatic life criteria would be appropriate to protect all 
applicable aquatic life designated uses, including any Federal 
designated use that the EPA may promulgate as part of a final rule.

VII. Conditions Where Federal Water Quality Standards Would Not Be 
Promulgated or Would Be Withdrawn

    As noted, under the CWA, states and authorized tribes have the 
primary responsibility for developing and adopting WQS for their 
navigable waters (CWA section 303(a) through (c)). Although the EPA is 
proposing a revised aquatic life designated use and protective 
dissolved oxygen criteria for the specified zones of the Delaware 
River, each state retains the option to adopt and submit to the EPA for 
review its own revised designated use and dissolved oxygen criteria 
that are consistent with CWA section 303(c) and the EPA's implementing 
regulation to address the EPA's Administrator's Determination.

A. Conditions Where Federal Standards Would Not Be Promulgated

    If Delaware, New Jersey, and Pennsylvania adopt and submit revised 
WQS that addresses the EPA's December 1, 2022, Administrator's 
Determination, and the EPA approves those WQS before finalizing this 
proposed rulemaking, then a Federal promulgation would no longer be 
required under the CWA. Similarly, if one state adopts and submits WQS 
consistent with this proposed rulemaking, and the EPA approves those 
WQS before finalizing this proposed rulemaking, then a Federal 
promulgation would no longer be required under the CWA for that state.

B. Conditions Where Federal Standards Would Be Withdrawn

    If the EPA finalizes this proposed rulemaking and Delaware, New 
Jersey, and Pennsylvania subsequently adopt and submit revised WQS to 
the EPA, and the EPA approves those WQS, then the EPA would undertake a 
rulemaking to withdraw the federally promulgated use and/or dissolved 
oxygen criteria (40 CFR 131.21(c)). Similarly, if one state adopts and 
submits revised WQS to the EPA, and the EPA approves those WQS, then 
the EPA would undertake a rulemaking to withdraw the federally 
promulgated WQS for that state.
    If Delaware's, New Jersey's, and/or Pennsylvania's adopted 
dissolved oxygen criteria are as stringent or more stringent than the 
federally promulgated criteria, then that state's criteria would 
immediately become the CWA-applicable criteria upon the EPA's approval. 
If Delaware's, New Jersey's, and/or Pennsylvania's adopted dissolved 
oxygen criteria are less stringent than the federally promulgated 
criteria, and the EPA approves those less stringent criteria, then 
those EPA-approved criteria would become the applicable criteria for 
CWA purposes only after the EPA withdraws its federally promulgated 
criteria for the relevant state(s).

[[Page 88329]]

VIII. Alternative Regulatory Approaches and Implementation Mechanisms

    The Federal WQS regulations at 40 CFR part 131 provide several 
approaches that Delaware, New Jersey, and Pennsylvania could use at 
each state's discretion when implementing or deciding how to implement 
the federally promulgated dissolved oxygen criteria, if finalized. The 
EPA has identified two approaches--WQS Variances and NPDES Permit 
Compliance Schedules--that might be of particular interest for the 
states covered by this proposed rulemaking. Additionally, the EPA 
included a discussion about CWA section 303(d)/305(b) water quality 
assessments to clarify potential options that may be available to 
states in the specific circumstances relevant to this rulemaking.

A. Water Quality Standards Variances

    A WQS variance is a time-limited designated use and criterion, for 
a specific pollutant or water quality parameter, that reflects the 
highest attainable condition (HAC) during the term of the WQS variance 
(40 CFR 131.3(o)). WQS variances can be used to incrementally improve 
water quality where the designated use and criterion are unattainable 
for a period of time. The state would need to demonstrate that 
attaining the applicable designated use and dissolved oxygen criterion 
would not be feasible for a period of time (i.e., during the term of 
the WQS variance) because of one of the factors specified in 40 CFR 
131.14(b)(2)(i)(A) and specify the actions that will be taken to make 
incremental water quality improvements during the term of the WQS 
variance.
    If Delaware, New Jersey, and/or Pennsylvania choose/s to adopt a 
WQS variance, the state/s must specify in the WQS variance the term and 
the interim requirements of the WQS variance. The term must be 
justified by describing the pollutant control activities expected to 
occur over that term to achieve the HAC. The interim requirements must 
be a quantitative expression that reflects the HAC using one of the 
options provided at 40 CFR 131.14(b)(1)(ii).
    WQS variances adopted in accordance with 40 CFR 131.14 and approved 
by the EPA for CWA purposes provide a legal avenue for states to write 
NPDES permit limits that are based on the HAC during the term of the 
WQS variance, while simultaneously implementing controls to make 
incremental water quality improvements toward ultimately attaining the 
applicable designated use and dissolved oxygen criterion.

B. NPDES Permit Compliance Schedules

    The EPA's regulations at 40 CFR 122.47 and 131.15 address how 
permitting authorities can use schedules for compliance with a water-
quality-based effluent limitation (WQBEL) in an NPDES permit, if the 
discharger needs time to undertake an enforceable sequence of actions--
such as facility upgrades or operation changes--leading to compliance 
with the WQBEL. The EPA's regulation at 40 CFR 122.47 allows states 
authorized to administer the NPDES program to include compliance 
schedules in NPDES permits, when appropriate and where authorized by 
the state's WQS, provided the compliance schedule authorizing provision 
was approved by the EPA. Such compliance schedules may be used to 
implement any CWA-effective WQS, including any WQS that the EPA 
promulgates as part of a final rule.

C. Clean Water Act Section 303(d)/305(b) Water Quality Assessments

    If the EPA promulgates revised aquatic life WQS for the specified 
zones of the Delaware River and they become effective for CWA purposes, 
Delaware, New Jersey, and Pennsylvania will have an obligation under 
CWA sections 303(d) and 305(b) to assess whether the WQS are being 
attained. The EPA anticipates there may be a period of time immediately 
after promulgation of the revised WQS when the WQS will not be attained 
because the actions and procedures required to achieve compliance will 
take time to implement. In this scenario, any of the relevant zones not 
attaining the WQS should be classified as impaired on the relevant 
303(d)/305(b) Integrated Report(s) (IR) that is submitted to the EPA 
for review.
    Per the CWA and the EPA's implementing regulations, waters that are 
assessed as impaired by a pollutant typically require the development 
of a Total Maximum Daily Load (TMDL), which is a regulatory planning 
tool designed to restore water quality via allocations of pollutant 
reductions to relevant point and non-point sources. The EPA regulations 
also recognize that other pollution control requirements may obviate 
the need for a TMDL. Specifically, impaired waters do not require a 
TMDL if: (1) technology-based effluent limitations required by the CWA; 
(2) more stringent effluent limitations required by a state, local, or 
Federal authority; or (3) other pollution control requirements (e.g., 
best management practices) required by a state, local, or Federal 
authority are stringent enough to implement applicable WQS (40 CFR 
130.7(b)(1)). Impaired waters that do not require a TMDL because they 
satisfy one of these alternatives are commonly referred to as Category 
4b waters, as described in the EPA's Integrated Reporting Guidance for 
CWA sections 303(d), 305(b), and 314.\77\
---------------------------------------------------------------------------

    \77\ The EPA's Integrated Reporting Guidance is available at: 
https://www.epa.gov/tmdl/integrated-reporting-guidance-under-cwa-sections-303d-305b-and-314.
---------------------------------------------------------------------------

    DRBC developed a model to evaluate sources of pollution that affect 
dissolved oxygen levels in the specified zones of the Delaware River 
and concluded that point sources are the primary contributor to oxygen 
depletion within those zones.\78\ DRBC therefore concluded that further 
controls on point sources are needed to achieve dissolved oxygen water 
quality conditions that support aquatic life designated uses that 
include propagation in the specified zones. The EPA's economic analysis 
evaluates point source controls that are expected to result in 
dissolved oxygen levels that meet EPA's proposed criteria.\79\ If, 
after finalization of this rulemaking, DRBC, Delaware, New Jersey, or 
Pennsylvania require effluent limitations and/or other pollution 
control requirements that the EPA agrees are stringent enough to 
implement the final dissolved oxygen criteria, the specified zones may 
be a candidate for Category 4b in future IRs. The EPA will work with 
Delaware, New Jersey, and Pennsylvania, in consultation with DRBC, on 
future IRs to determine the appropriate assessment status for the 
waters that are subject to this rulemaking.
---------------------------------------------------------------------------

    \78\ Delaware River Basin Commission (2022a, 2022b).
    \79\ More details are available in the document, Economic 
Analysis for the Proposed Rule: Water Quality Standards to Protect 
Aquatic Life in the Delaware River.
---------------------------------------------------------------------------

IX. Economic Analysis

    The EPA conducted an economic analysis to evaluate the potential 
costs and benefits associated with this proposed rulemaking. In the 
high-level summary of the EPA's economic analysis below, the EPA first 
describes a baseline scenario that is intended to characterize the 
world in the absence of the EPA's proposed rule. Next, the EPA 
describes development of a policy scenario based on potential pollution 
control actions that, if implemented, can be expected to meet the EPA's 
proposed dissolved oxygen criteria. Finally, the EPA evaluates the 
anticipated costs and benefits associated with the policy scenario and 
the EPA's proposed criteria. More details and information

[[Page 88330]]

are available in the associated document, Economic Analysis for the 
Proposed Rule: Water Quality Standards to Protect Aquatic Life in the 
Delaware River.

A. Baseline for the Analysis

    The baseline is intended to characterize the world in the absence 
of the EPA's proposed rule. The EPA typically assumes full compliance 
with existing regulations and requirements--including CSO long-term 
control plans (LTCPs)--even if they are not yet fully implemented, as a 
basis for estimating the cost and benefits of proposed regulations. 
This baseline approach ensures that the cost and benefits of the 
existing regulations and requirements are not double counted.
    In this economic analysis, the EPA assumes that without the 
proposed rule, the less stringent WQS (that do not support aquatic life 
propagation) currently in effect for CWA purposes would remain in 
effect (section III.D. of this preamble). Accordingly, the EPA assumes 
that water quality conditions in the specified zones of the Delaware 
River, particularly during the Juvenile Development season (July 1-
October 31), would continue to experience low oxygen levels that do not 
support aquatic life propagation, even with implementation of existing 
and planned CSO LTCPs.\80\ Along the specified zones of the Delaware 
River, there are three combined sewer systems with CSO LTCPs that are 
relevant for consideration by the EPA as part of the baseline. The 
Philadelphia Water Department, Camden County Municipal Utilities 
Authority, and Delaware County Regional Water Quality Control Authority 
all have LTCPs that are either approved or in progress.\81\ The EPA 
expects implementation of these LTCPs, when finalized, to occur 
regardless of the EPA's proposed rule. Therefore, the EPA included 
estimated CSO volume reductions for these three dischargers as part of 
the baseline for this economic analysis.
---------------------------------------------------------------------------

    \80\ While the EPA normally assumes full compliance with 
existing LTCPs, for this proposed rulemaking, the EPA is also 
assuming full compliance with planned LTCPs. Because planned LTCPs 
are not final and therefore are subject to change, this adds 
uncertainty to the baseline conditions.
    \81\ Delaware River Basin Commission (2022a); DELCORA. (2023). 
Combined Sewer System: DELCORA CSO LTCP. https://www.delcora.org/combined-sewer-systems/delcora-cso-ltcp/; Philadelphia Water 
Department. (2023). CSO Long Term Control Plan. https://water.phila.gov/reporting/ltcp/; State of New Jersey Division of 
Water Quality. (2023). Long Term Control Plan Submittals. https://www.nj.gov/dep/dwq/cso-ltcpsubmittals.htm.
---------------------------------------------------------------------------

    DRBC modeled the effect of pollution reduction on dissolved oxygen 
levels in the Delaware River and provided the EPA with water quality 
simulation results under both baseline and ``restored'' conditions for 
the years 2012, 2018, and 2019.\82\ Baseline simulations predict water 
quality conditions associated with the discharge of actual wastewater 
treatment plant (WWTP) flows at existing levels of treatment and after 
full implementation of LTCPs. The restored simulations predict water 
quality conditions associated with the discharge of actual WWTP flows 
at treatment levels that include additional effluent treatment and 
after full implementation of LTCPs.
---------------------------------------------------------------------------

    \82\ The EPA determined that the model runs from DRBC were 
sufficient for use in this economic analysis.
---------------------------------------------------------------------------

    Of the three available years (2012, 2018, and 2019), the EPA 
selected the 2019 year as representative of the most typical conditions 
in the relevant zones of the Delaware River. In comparison, 2012 had 
atypically poor conditions (low percent oxygen saturation, high water 
temperature), while 2018 had atypically good conditions (high percent 
oxygen saturation, low water temperature). Therefore, model runs used 
in this economic analysis are based on 2019 conditions.

B. Development of the Policy Scenario

    There is a wide range of potential paths that Delaware, New Jersey, 
and Pennsylvania may choose to take when implementing the EPA's 
proposed WQS. For this economic analysis, the EPA relied on available 
data to develop a policy scenario based on modeled pollution controls 
developed by DRBC that the EPA expects would meet the Agency's proposed 
dissolved oxygen criteria. Actual benefits, costs, and impacts will 
depend on the choices that states would make in implementing the 
proposed WQS, which may differ from the policy scenario in this 
economic analysis.
    The EPA's proposed dissolved oxygen criteria apply to three seasons 
(section IV.C. of this preamble). Therefore, when developing a policy 
scenario for this proposed rulemaking, the EPA evaluated potential 
pollution control actions that would be expected to meet the EPA's 
criteria in each of the three seasons. The EPA began by evaluating 
water quality monitoring data for the past decade from two continuous 
monitoring stations in the relevant zones of the Delaware River--Penn's 
Landing in Zone 3 and Chester in Zone 4. Based on the monitoring data, 
the EPA expects that the Agency's proposed dissolved oxygen criteria 
for the Spawning and Larval Development and Overwintering seasons will 
likely be met without the need for additional WWTP upgrades or other 
controls beyond the baseline conditions (i.e., the LTCPs). Monitoring 
data for the Juvenile Development season indicated that additional 
pollution control actions are likely necessary to meet the EPA's 
proposed criteria in that season. To develop a policy scenario for the 
Juvenile Development season, the EPA relied on modeled data from DRBC 
predicting oxygen levels in 2019 in the specified zones of the Delaware 
River following a set of WWTP pollution control actions for certain 
dischargers. Modeled data for restored conditions are described in the 
baseline section above, while WWTP controls are described in the cost 
section below. The EPA expects that this policy scenario (hereafter, 
the ``2019 restored scenario'') will meet the proposed criteria during 
the Juvenile Development season.

C. Potential Costs

    The EPA estimated compliance costs for the proposed WQS based on 
estimates for WWTPs to reduce effluent ammonia nitrogen concentrations 
and raise effluent dissolved oxygen concentrations. Although there are 
several causes that contribute to low dissolved oxygen conditions in 
the specified zones of the Delaware River, DRBC identified ammonia 
nitrogen loadings from WWTPs as the leading cause of oxygen-depletion 
in the river.\83\ As a result, for the purpose of this economic 
analysis, the EPA assumed that additional pollution control 
technologies implemented at WWTPs is the most likely way that Delaware, 
New Jersey, and Pennsylvania will implement the proposed WQS. 
Therefore, the EPA evaluated WWTP controls rather than other non-point 
source controls for this cost analysis.
---------------------------------------------------------------------------

    \83\ Delaware River Basin Commission (2022a).
---------------------------------------------------------------------------

    The EPA relied on cost information from several DRBC studies to 
estimate the costs of achieving the proposed WQS.\84\ DRBC's 2022 
Analysis of Attainability report categorized WWTPs as either class A', 
A, or B facilities. DRBC determined that discharges from Class A', A, 
and B facilities have a major

[[Page 88331]]

impact, a marginal impact, or no measurable impact on oxygen levels in 
the specified zones, respectively. The EPA's 2019 restored scenario 
follows DRBC's approach by including the seven Class A' and two Class A 
facilities and excluded the three Class B facilities.\85\
---------------------------------------------------------------------------

    \84\ Id.; Kleinfelder Inc. (2021). Nitrogen Reduction Cost 
Estimation Study Final Summary Report. https://www.nj.gov/drbc/library/documents/NitrogenReductionCostEstimates_KleinfelderJan2021.pdf; Kleinfelder 
Inc. (2023). Delaware River Basin Commission Nitrogen Reduction Cost 
Estimation Study--Supplemental Cost Addendum 2 Technical 
Memorandum--Final. https://www.nj.gov/drbc/library/documents/NitrogenReductionCostEstimates_Kleinfelder_aug2023addendum.pdf.
    \85\ Delaware River Basin Commission (2022a).
---------------------------------------------------------------------------

    The EPA used WWTP-specific (capital, operations and maintenance 
(O&M)) compliance costs from Kleinfelder Inc. (2021, 2023) to estimate 
compliance costs, based on the discharger classification. Total 
compliance costs include the costs associated with both of the 
following:
    1. Class A' Facilities: Costs associated with reductions in 
effluent ammonia nitrogen concentrations to 1.5 mg/L from May 1 through 
October 31 and increases in effluent oxygen concentrations to a monthly 
average of 6 mg/L year-round for the seven WWTPs categorized as Class 
A' facilities.
    2. Class A Facilities: Costs associated with reductions in effluent 
ammonia nitrogen concentrations to 5 mg/L from May 1 through October 31 
for the two WWTPs categorized as Class A facilities.
    To estimate annualized compliance costs, the EPA assumed capital 
costs occur upfront in 2024 followed by a 5-year construction period. 
Consistent with Kleinfelder Inc. (2021, 2023), the EPA assumed O&M 
costs occur over a 25-year period from 2029 through 2053. The EPA thus 
annualized costs over a 30-year analysis period between 2024 and 2053 
and discounted all cost values to 2024, using a 3 percent discount 
rate.
    Table 10 of this preamble presents the annualized compliance costs 
associated with achieving the EPA's proposed WQS, using a 3 percent 
discount rate. The estimated total annualized compliance cost across 
nine WWTPs is $137.1 million (2022$). These costs vary considerably 
between the nine WWTPs, ranging from $1.9 million at the Lower Bucks 
County Joint Municipal Authority WWTP to $37.6 million at the 
Philadelphia Water Department (PWD) Southwest Water Pollution Control 
Plant (2022$). Among the dischargers, PWD bears the highest proportion 
of total costs, with its three facilities' combined costs accounting 
for over 50 percent of total costs. Overall, 66 percent of the costs 
are attributable to capital and 34 percent are attributable to O&M.

                      Table 10--Annualized Compliance Costs Using a 3 Percent Discount Rate
                                                 [Million 2022$]
----------------------------------------------------------------------------------------------------------------
                                                                                                Annualized costs
                Plant                             State                       Class             (millions 2022$)
----------------------------------------------------------------------------------------------------------------
Camden County Municipal Utilities      NJ........................  A'........................              $16.2
 Authority.
City of Wilmington...................  DE........................  A'........................               23.9
Delaware County Regional Water         DE........................  A'........................                9.1
 Pollution Control Authority.
Gloucester County Utilities Authority  NJ........................  A'........................                4.9
PWD Northeast Water Pollution Control  PA........................  A'........................               26.2
 Plant.
PWD Southeast Water Pollution Control  PA........................  A'........................               14.1
 Plant.
PWD Southwest Water Pollution Control  PA........................  A'........................               37.6
 Plant.
Hamilton Township....................  NJ........................  A.........................                3.3
Lower Bucks County Joint Municipal     PA........................  A.........................                1.9
 Authority.
                                                                                              ------------------
    Total............................  ..........................  ..........................              137.1
----------------------------------------------------------------------------------------------------------------

D. Potential Benefits

    Water quality improvements can have a wide range of effects on 
water resources and the environmental goods and services that they 
provide, including services valued by people (e.g., recreation, 
commercial fishing, public and private property ownership, existence 
services such as aquatic life, wildlife, and habitat designated uses). 
Some environmental goods and services (e.g., commercially caught fish) 
are traded in markets, and thus their value can be directly observed. 
Other environmental goods and services (e.g., recreation and support of 
aquatic life) cannot be bought or sold directly and thus do not have 
observable market values. This second type of environmental goods and 
services are classified as ``non-market.'' The estimated changes in the 
non-market values of the water resources affected by the EPA's proposed 
WQS (hereafter, ``non-market benefits'') are additive to market values 
(e.g., avoided costs of producing various market goods and services).
    To value non-market benefits, the EPA used a benefit transfer 
approach based on a meta-analysis of surface water valuation studies to 
evaluate the use and nonuse benefits of improved surface water quality 
resulting from achievement of the EPA's proposed WQS in the 2019 
restored scenario.\86\ The benefit transfer approach involves three 
main steps:
---------------------------------------------------------------------------

    \86\ The EPA has used this benefit transfer approach on numerous 
occasions, most recently in the Benefit and Cost Analysis for 
Proposed Revisions to the Effluent Limitations Guidelines and 
Standards for the Steam Electric Power Generating Point Source 
Category, which is available at https://www.epa.gov/system/files/documents/2023-03/steam-electric-benefit-cost-analysis_proposed_feb-2023.pdf.
---------------------------------------------------------------------------

    1. Estimating water quality improvements associated with attainment 
of the EPA's proposed WQS relative to the baseline;
    2. Translating these improvements into a water quality index (WQI) 
that can be linked to ecosystem services and uses that are valued by 
society. The WQI used for this analysis includes six parameters: 
dissolved oxygen, biological oxygen demand (BOD), fecal coliform (FC), 
total nitrogen (TN), total phosphorus (TP), and total suspended solids 
(TSS); and
    3. Estimating the dollar value of the estimated water quality 
improvements based on estimates of the public's willingness-to-pay 
(WTP) derived from a meta-analysis of surface water valuation studies.
    To estimate changes in ecosystem services provided in the specified 
zones of the Delaware River following attainment of the proposed WQS, 
the EPA obtained water quality modeling data from DRBC, including 
dissolved oxygen, TN, and TP levels for various effluent treatment 
scenarios. The EPA used DRBC's modeled output of dissolved oxygen 
levels in the specified zones following implementation of effluent 
controls (described in the cost section) and based on 2019 conditions 
(as described in the policy scenario

[[Page 88332]]

section). The EPA used the 2019 restored scenario as the basis for 
representing conditions following the implementation of the proposed 
WQS, while making minor adjustments as needed \87\ to ensure that 
predicted oxygen levels meet the EPA's proposed WQS. This analysis 
provides insight into the water quality improvements and benefits that 
are likely to result from implementation of the proposed WQS. For the 
remaining parameters included in the WQI (i.e., BOD, FC, and TSS), the 
EPA relied on measured data at various locations within the specified 
zones.
---------------------------------------------------------------------------

    \87\ Adjustments are detailed in section 4.2 of the associated 
document, Economic Analysis for the Proposed Rule: Water Quality 
Standards to Protect Aquatic Life in the Delaware River.
---------------------------------------------------------------------------

    The effluent treatment measures implemented in response to the 
proposed WQS would directly affect the amount of ammonia nitrogen 
discharged to the specified zones of the Delaware River and therefore 
also reduce BOD. However, DRBC's model does not account for the changes 
in BOD. The EPA approximated BOD concentrations following effluent 
treatment by assuming that baseline BOD concentrations are reduced by 
the same percentage change that dissolved oxygen improves within each 
zone (i.e., Zone 3, 4, and Upper 5) of the model. The EPA kept levels 
for the remaining parameters (TN, TP, TSS, and FC) unchanged from 
baseline conditions.
    Table 11 of this preamble summarizes the percent change in 
dissolved oxygen and BOD by zone between the baseline and the 2019 
restored scenario.

 Table 11--Dissolved Oxygen and Biological Oxygen Demand Changes Between
                the Baseline and 2019 Restored Scenarios
------------------------------------------------------------------------
                                                          Percent change
                          Zone                             from baseline
                                                                \a\
------------------------------------------------------------------------
3.......................................................            10.8
4.......................................................            23.8
Upper-5.................................................             8.8
------------------------------------------------------------------------
\a\ The percent change for dissolved oxygen and biological oxygen demand
  are the same, but in opposite directions, i.e., the percent decrease
  in biological oxygen demand concentration is the same as the percent
  increase in dissolved oxygen concentration.

    To quantify benefits of water quality improvements, as is 
consistent with past practice, the EPA analyzed the values held by 
households residing within 100 miles of the specified zones of the 
Delaware River for water quality improvements associated with the EPA's 
proposed WQS.\88\ Households may consider waters unaffected by the 
EPA's proposed WQS to be substitute waters for those affected, and this 
can influence what households would be willing to pay for improvements 
associated with the proposed WQS. The EPA deems waters unaffected by 
the proposed WQS within the 100-mile buffer around each Census block 
group as viable substitutes.
---------------------------------------------------------------------------

    \88\ The EPA's 100-mile radius assumption follows Viscusi et al. 
(2008), which states: `The survey defined relevant water quality as 
residing in a region that is ``a 2-hour drive or so of your home, in 
other words, within 100 miles.'' About 80% of all recreational uses 
of bodies of water are within such a radius of users' homes. This 
80% figure was based on data generated by EPA from the 1996 National 
Survey on Recreation and the Environment. Data indicates that 77.9% 
of boating visits, 78.1% of fishing visits, and 76.9% of swimming 
recreational visits are within a 100-mile radius of a given 
waterbody. (Citation: Viscusi, W. K., Huber, J., & Bell, J. (2008). 
The economic value of water quality. Environmental and resource 
economics, 41(2), 169-187.)
---------------------------------------------------------------------------

    The EPA estimated the economic value of water quality changes using 
results of a meta-analysis of 189 estimates of total WTP (including 
both use and nonuse values) for water quality improvements, provided by 
59 original studies conducted between 1981 and 2017. The estimated 
econometric model allows calculation of total WTP for changes in a 
variety of environmental services affected by water quality and valued 
by people, including changes in recreational fishing opportunities, 
other water-based recreation, and existence services such as aquatic 
life, wildlife, and habitat designated uses. The model also allows the 
EPA to adjust WTP values based on the core geospatial factors predicted 
by theory to influence WTP, including: scale (the size of affected 
resources or areas), market extent (the size of the market area over 
which WTP is estimated), and the availability of substitute waters. The 
model also takes into account important sociodemographic 
characteristics, such as population and income, which vary spatially.
    Table 12 in this preamble presents estimated household and total 
annualized WTP value for water quality improvements following 
attainment of the EPA's proposed WQS, based on a 3 percent discount 
rate. The total annualized value of water quality improvements from 
attainment of the proposed WQS is $112.8 million.

  Table 12--Estimated Household and Total Annualized Willingness-to-Pay
   (WTP) for Water Quality Improvements Under the EPA's Proposed Water
           Quality Standards, Using a 3 Percent Discount Rate
------------------------------------------------------------------------
                                                              Total
                                        Average  annual   annualized WTP
 Average number of affected households      WTP per         (millions
              (millions)                   household        2022$, 3%
                                            (2022$)       discount rate)
------------------------------------------------------------------------
14.96.................................           $8.18           $112.8
------------------------------------------------------------------------

E. Conclusion

    The United States Office of Management and Budget requires that for 
``significant regulatory actions'' (as defined in Executive Order 12866 
and as amended and reaffirmed by Executive Order 14094), that the EPA 
conduct an economic analysis. While this proposed rulemaking was not 
deemed significant, the EPA nonetheless conducted an economic analysis 
to evaluate the potential costs and benefits associated with the WQS in 
the EPA's proposed rule. For this proposed rulemaking, the EPA 
determined that the potential benefits justify the potential costs. The 
EPA estimates that the implementation of additional effluent treatment 
controls at certain WWTPs could lead to $137.1 million in annualized 
costs over 30 years (2022$, 3% discount rate). The EPA quantified 
estimated non-market benefits through average annual household WTP for 
water quality improvements. Annualized non-market benefits total $112.8 
million per year over 30 years (2022$, 3% discount rate). The EPA's 
monetary estimation of benefits does not account for benefits related 
to protections for a critically endangered species (Atlantic Sturgeon), 
increased housing values, or increased commercial fishing, among other 
benefits. Therefore, the EPA's estimation of non-market benefits is 
likely an underestimate of total benefits and thus total benefits could 
potentially equal or exceed estimated total costs.

X. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 14094: Modernizing Regulatory Review

    This action is not a significant regulatory action as defined in 
Executive Order 12866, as amended by Executive Order 14094, and was 
therefore not subject to a requirement for Executive Order 12866 
review.

[[Page 88333]]

B. Paperwork Reduction Act (PRA)

    This action does not impose any new information collection burden 
under the PRA. OMB has previously approved the information collection 
activities contained in the existing regulations and has assigned OMB 
control number 2040-0049. While actions to implement these WQS, if 
finalized, could entail additional paperwork burden, this action does 
not directly contain any information collection, reporting, or record-
keeping requirements.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. This 
action will not impose any requirements on small entities. Small 
entities, such as small businesses or small governmental jurisdictions, 
are not directly regulated by this rulemaking.
    EPA-promulgated WQS are implemented through various water quality 
control programs including the NPDES program, which limits discharges 
to navigable waters, except in compliance with a NPDES permit. CWA 
section 301(b)(1)(C) and the EPA's implementing regulations at 40 CFR 
122.44(d)(1) and 122.44(d)(1)(A) provide that all NPDES permits must 
include any limits on discharges that are necessary to meet applicable 
WQS. Thus, under the CWA, the EPA's promulgation of WQS establishes 
standards that states implement through the NPDES permit process. While 
states have discretion in developing discharge limits, those limits 
``must control all pollutants or pollutant parameters (either 
conventional, nonconventional, or toxic pollutants) which the Director 
determines are or may be discharged at a level that will cause, have 
the reasonable potential to cause, or contribute to an excursion above 
any [s]tate water quality standard, including [s]tate narrative 
criteria for water quality'' (40 CFR 122.44(d)(1)(i)).
    As a result of this action, if finalized, the states of Delaware, 
New Jersey, and Pennsylvania will need to ensure that permits they 
issue include any limitations on discharges necessary to comply with 
the WQS established in the final rule. In doing so, each state will 
have several choices associated with permit writing. While each state's 
implementation of the rule may ultimately result in new or revised 
permit conditions for some dischargers, including small entities, the 
EPA's action, by itself, does not impose any of these requirements on 
small entities; in other words, these requirements are not self-
implementing.

D. Unfunded Mandates Reform Act (UMRA)

    This action does not contain any unfunded mandate as described in 
UMRA, 2 U.S.C. 1531-1538, and does not significantly or uniquely affect 
small governments. The action imposes no enforceable duty on any state, 
local, or Tribal governments or the private sector.

E. Executive Order 13132: Federalism

    The EPA has concluded that this action does not have federalism 
implications. It will not have substantial direct effects on the 
states, on the relationship between the national government and the 
states, or on the distribution of power and responsibilities among the 
various levels of government. This rulemaking would not alter 
Delaware's, New Jersey's, or Pennsylvania's considerable discretion in 
implementing these WQS, nor would it preclude any of those states from 
adopting revised WQS and submitting them to the EPA for review and 
approval either before or after promulgation of the final rule. If the 
states submit and the EPA approves revised WQS consistent with the CWA, 
then the EPA would no longer be required to promulgate Federal WQS.
    Consistent with the EPA's policy to promote communications between 
the EPA and state and local governments, the EPA met with the states of 
Delaware, New Jersey, and Pennsylvania and DRBC in the process of 
developing this rulemaking to enable them to have meaningful input into 
its development. During these discussions, the EPA explained the 
scientific basis for the dissolved oxygen criteria to protect aquatic 
life propagation in the specified zones of the Delaware River and the 
overall timing of the Federal rulemaking effort. The EPA took these 
discussions with the states into account during the drafting of this 
rulemaking. The EPA specifically solicits comments on this proposed 
action from state and local officials.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have Tribal implications as specified in 
Executive Order 13175. This rulemaking will not affect federally 
recognized Indian tribes in Delaware, New Jersey, or Pennsylvania 
because the WQS would not apply to waters in Indian lands nor affect 
Tribal interests. Thus, Executive Order 13175 does not apply to this 
action.

G. Executive Order 13045: Protection of Children From Environmental 
Health and Safety Risks

    The EPA interprets Executive Order 13045 as applying only to those 
regulatory actions considered significant under section 3(f)(1) of 
Executive Order 12866 and that concern environmental health or safety 
risks that the EPA has reason to believe may disproportionately affect 
children, per the definition of ``covered regulatory action'' in 
section 2-202 of the Executive order. Therefore, this action is not 
subject to Executive Order 13045 because it does not concern an 
environmental health risk or safety risk. Since this action does not 
concern human health, the EPA's Policy on Children's Health also does 
not apply.

H. Executive Order 13211: Actions That Significantly Affect Energy 
Supply, Distribution, or Use

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. This action proposes to establish 
Federal CWA aquatic life water quality criteria for specified zones of 
the Delaware River under the jurisdiction of the states of Delaware, 
New Jersey, and Pennsylvania.

I. National Technology Transfer and Advancement Act (NTTAA)

    This rulemaking does not involve technical standards.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations and 
Executive Order 14096: Revitalizing Our Nation's Commitment to 
Environmental Justice for All

    The information supporting this Executive order review is 
summarized below and detailed in the associated document, Environmental 
Justice Analysis for the Proposed Rule: Water Quality Standards to 
Protect Aquatic Life in the Delaware River, which is available in the 
docket for this proposed rule.
    The EPA believes that the human health or environmental conditions 
that exist prior to this proposed action result in or have the 
potential to result in disproportionate and adverse human health or 
environmental effects on communities with environmental justice (EJ) 
concerns. For this EJ analysis, the EPA evaluated socioeconomic 
characteristics of communities living near the relevant zones of the 
Delaware River compared to communities living near other zones of the 
mainstem

[[Page 88334]]

Delaware River. The relevant zones of the Delaware River border highly 
urbanized areas, including cities such as Philadelphia and Wilmington. 
Accordingly, the EPA's analysis accounts for the distinction between 
urban and rural communities.\89\
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    \89\ For this analysis, the EPA defines ``urban'' and ``rural'' 
using the Census Urban Areas designation. More information about the 
Census classifications is available at https://www.census.gov/programs-surveys/geography/guidance/geo-areas/urban-rural.html.
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    The EPA obtained data from the United States Census Bureau's 
American Community Survey (ACS) 5-year estimates for the years 2017-
2021 at the Census block group level to construct a set of eight 
metrics for use in this analysis: (1) Black or African American, (2) 
Asian, (3) Two or More Races, (4) Hispanic or Latino, (5) Limited 
English Speaking Household, (6) Median Household Income, (7) Below 200% 
of the Poverty Level, (8) Education Less than a High School Diploma or 
Equivalent.\90\ Analysis of these eight socioeconomic metrics provides 
insight into the spatial distribution and prevalence of certain 
indicators of social vulnerability for communities near the Delaware 
River.\91\
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    \90\ The EPA also considered populations who identify as 
American Indian and Alaskan Native, Native Hawaiian and Other 
Pacific Islander, and Some Other Race; however, in the Delaware 
River watershed, these populations represent a very small fraction 
(often less than 1%) of the community composition. Therefore, these 
populations are not analyzed further in this EJ analysis.
    \91\ In the 2016 Technical Guidance for Assessing Environmental 
Justice in Regulatory Analysis, the EPA defined vulnerability as the 
``physical, chemical, biological, social, and cultural factors that 
result in certain communities and population groups being more 
susceptible or more exposed to environmental toxins, or having 
compromised ability to cope with and/or recover from such 
exposure.'' For this EJ analysis, the EPA focused on social 
vulnerability based on the metrics presented in table 3 of the 
associated environmental justice analysis, which broadly cover 
categories of race, ethnicity, linguistic isolation, income, 
poverty, and education. These metrics provide insight into factors 
that may affect the ability of communities near the Delaware River 
to respond to environmental hazards or cope with reduced ecosystem 
services that may result from inadequate water quality. Although 
these socioeconomic metrics are relevant to communities living near 
the Delaware River, they are not intended to be an exhaustive list 
of all factors affecting community vulnerability. (Source: United 
States Environmental Protection Agency. (2016). Technical Guidance 
for Assessing Environmental Justice in Regulatory Analysis. https://www.epa.gov/sites/default/files/2016-06/documents/ejtg_5_6_16_v5.1.pdf.)
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    The EPA extended a five-mile buffer from the specified zones to 
capture communities living in close proximity to waters affected by the 
EPA's proposed rule, if finalized.\92\ Similarly, the EPA extended a 
five-mile buffer from other zones of the Delaware River to form a 
comparison group. Given the large number of block groups located near 
the mainstem Delaware River, communities are analyzed in groups, as 
follows:
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    \92\ The EPA assumes that those living in Census block groups 
that are within the five-mile buffer, and therefore closest to the 
specified zones of the Delaware River, are most likely to be 
directly affected by the proposed rule. However, this assumption 
could underestimate directly affected communities and impact the 
results of the proximity analysis. Accordingly, the EPA conducted a 
sensitivity analysis using a ten-mile buffer and determined that 
community composition was not particularly sensitive to the buffer 
distance applied when comparing the results of the five-mile and 
ten-mile buffer.
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     Delaware Urban Areas: Census block groups in urban areas 
within five miles of the specified zones in Delaware.
     New Jersey Urban Areas: Census block groups in urban areas 
within five miles of the specified zones in New Jersey.
     Pennsylvania Urban Areas: Census block groups in urban 
areas within five miles of the specified zones in Pennsylvania.
     Urban Comparison Group: Census block groups in urban areas 
within five miles of the remainder of the mainstem Delaware River 
(i.e., excluding block groups within five miles of the specified 
zones).
     Specified Zones Rural Areas: Census block groups in rural 
areas within five miles of the specified zones in New Jersey.\93\
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    \93\ There are no rural areas within five miles of the specified 
zones in Delaware or Pennsylvania.
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     Rural Comparison Group: Census block groups in rural areas 
within five miles of the remainder of the mainstem Delaware River 
(i.e., excluding block groups within five miles of the specified 
zones).
    The EPA aggregated data across multiple block groups using aerial 
apportionment and a population-weighted mean approach to ensure that 
block groups with larger or smaller populations were accounted for 
proportionally to their size. This calculation relies on an assumption 
that households are evenly distributed within each block group. For 
Median Household Income, the EPA aggregated data across multiple block 
groups using a linear interpolation calculation.
    The results of the urban and rural proximity analyses differed 
significantly. Urban communities in Pennsylvania near the specified 
zones surpassed the comparison group average (or were less than the 
comparison group for Median Household Income) for all eight 
socioeconomic metrics. Notably, urban communities in Pennsylvania near 
the specified zones are over 1.7 times more likely to identify as Black 
or African American, 1.7 times more likely to live below twice the 
poverty level, and have $23,000 lower median household income when 
compared to urban communities near the remainder of the mainstem river. 
Urban communities within five miles of the specified zones in all three 
states had lower income and higher poverty rates than the comparison 
group. Urban communities in Delaware near the specified zones also had 
a higher percentage of the population identify as Black or African 
American than the comparison group, while urban communities in New 
Jersey had a higher percentage of the population that identifies as 
Hispanic or Latino and a greater percentage with education less than a 
high school degree than the comparison group. Therefore, urban 
communities near the specified zones--especially in Pennsylvania--
exhibited differences in socioeconomic community characteristics 
compared to other urban communities near the Delaware River.
    On the other hand, rural communities near the specified zones did 
not greatly differ from rural communities near other parts of the 
mainstem river. While rural communities near the specified zones did 
exceed the comparison group average for four metrics (Black or African 
American, Asian, Two or More Races, and Limited English Speaking 
Household), the differences were always less than three percentage 
points. Therefore, the EPA could not conclude that rural communities 
near the specified zones were any more or less socially vulnerable 
compared to other rural communities near the mainstem Delaware River.
    While neither the urban nor the rural proximity analyses directly 
indicate which communities may be experiencing potential EJ concerns, 
they provide insight into community composition surrounding an 
environmental resource. In general, the Delaware River has had two 
contrasting areas of water quality for decades. In the relevant zones, 
water quality for aquatic life has been significantly worse than in the 
other zones of the river.\94\ Urban areas near these zones, especially 
in Pennsylvania, contain communities that are likely more socially 
vulnerable than urban communities that live near other zones of the 
Delaware River, which have better water quality. This trend in water 
quality and dissolved oxygen across the watershed, coupled with the 
corresponding differences in socioeconomic community composition, 
reveals a potential inequitable

[[Page 88335]]

distribution of an environmental resource and access to clean surface 
waters within a single watershed.\95\
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    \94\ Delaware River Basin Commission (2022a).
    \95\ In this analysis, the EPA is not implying causality between 
poor water quality and socioeconomic factors.
---------------------------------------------------------------------------

    The EPA believes that this action would be likely to reduce 
existing disproportionate and adverse effects on communities with EJ 
concerns. Specifically, the EPA identified an inequitable distribution 
of an environmental resource where communities with environmental 
justice concerns have inequitable access to clean surface waters that 
support CWA section 101(a)(2) goals for aquatic life. The EPA's 
proposed rule, if finalized and implemented, could help to lessen this 
inequitable distribution of an environmental resource by ensuring that 
WQS to protect aquatic life in the specified zones of the Delaware 
River meet the objectives of the CWA.
    In addition to the proximity analysis, the EPA evaluated the 
potential distribution of costs associated with the proposed rule under 
the implementation (policy) scenario described in section IX of this 
preamble and further detailed in the EPA's associated document, 
Economic Analysis for the Proposed Rule: Water Quality Standards to 
Protect Aquatic Life in the Delaware River. For this analysis, the EPA 
selected Philadelphia as a case study based on the results of the 
proximity analysis and the large share of total estimated costs 
potentially incurred by the Philadelphia Water Department (PWD) 
compared to other WWTPs.
    The EPA used two methods to assess the potential financial impact 
to Philadelphia households resulting from costs associated with the 
proposed rule. First, the EPA calculated household burden by 
quantifying the potential increase to consumer water and wastewater 
bills and calculating the percentage of median household income spent 
on water bills with and without costs from additional wastewater 
treatment plant controls. Second, the EPA examined existing water rate 
structures in Philadelphia and customer assistance programs to identify 
possible ways in which the affected municipalities could adjust rates 
to lessen the financial burden on low-income households.
    To determine household burden, the EPA analyzed how annual water 
and wastewater bills might change if costs associated with additional 
wastewater treatment plant controls at PWD facilities are passed on to 
households through increased water bills.\96\ The EPA analyzed the 
financial impact to households if costs were passed on to residential 
households in proportion to the estimated wastewater flow attributed to 
residential households.\97\ DRBC estimates that approximately 15% of 
the flow to PWD is attributable to residential sources while 85% is 
attributable to non-residential sources.\98\ Therefore, the EPA 
calculated household burden assuming 15% of the costs associated with 
additional wastewater treatment plant controls would be spread evenly 
among Philadelphia households. Under this assumption the additional 
annual cost per household is $18.07, which would equate to $1.50 per 
household per month.\99\ For this analysis, the EPA analyzed household 
burden using the Residential Indicator in the EPA's 2023 Clean Water 
Act Financial Capability Assessment Guidance \100\ and determined that 
while the costs associated with the proposed rule are not expected to 
substantially impact household burden under this scenario, water bills 
still have the potential to be placing a high burden on a third of 
Philadelphia's households. However, the actual financial burden faced 
by households depends on many factors, including customer assistance 
programs.
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    \96\ Residents in PWD's service area pay a single bill that 
covers both water and wastewater charges; for this analysis, the EPA 
uses the term ``water bill'' to refer to the single bill covering 
water and wastewater charges.
    \97\ The EPA also analyzed a conservative scenario in which 100% 
of costs are passed on to residential households. Results of this 
scenario are available in the associated document, Environmental 
Justice Analysis for the Proposed Rule: Water Quality Standards to 
Protect Aquatic Life in the Delaware River.
    \98\ Delaware River Basin Commission. (2022c). Social and 
Economic Factors Affecting the Attainment of Aquatic Life Uses in 
the Delaware River Estuary. September 2022 Draft. https://www.nj.gov/drbc/library/documents/AnalysisAttainability/SocialandEconomicFactors_DRAFTsept2022.pdf.
    \99\ As of September 1, 2023, the monthly water bill for a 
typical residential consumer in Philadelphia is $74.81, which 
equates to $897.72 annually. Source: Philadelphia Water Department. 
Rate Changes Effective September 2023. Web page, accessed September 
26, 2023. https://water.phila.gov/drops/new-rate-information-effective-september-2023/.
    \100\ United States Environmental Protection Agency. (2023). 
Clean Water Act Financial Capability Assessment Guidance. Document 
ID: 800b21001. February 2023. https://www.epa.gov/system/files/documents/2023-01/cwa-financial-capability-assessment-guidance.pdf.
---------------------------------------------------------------------------

    In July 2017, Philadelphia became the first to implement an income-
based alternative water rate structure through creation of the Tiered 
Assistance Program (TAP). This program is structured based on household 
income relative to the Federal poverty level such that monthly bills 
are capped at 2%, 2.5%, 3%, and 4% of monthly income for consumers 
whose income is 0-50%, >50-100%, >100-150%, and >150% of the Federal 
poverty level, respectively.\101\ TAP discounts are offset by a 
surcharge added to the water bill of non-TAP customers.
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    \101\ City of Philadelphia. (2023). Annual Report to the Mayor 
on the Tiered Assistance Program (TAP). Department of Revenue. March 
31, 2023. https://www.phila.gov/media/20230526113411/Tiered-Assistance-Program-TAP-2022-annual-report.pdf.
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    For illustrative purposes, the EPA analyzed how the TAP rate 
structure might apply to eligible low-income consumers with water bills 
that include 15% of the costs associated with additional PWD wastewater 
treatment plant controls.\102\ Under the TAP rate structure, a three-
person household with income at or below the poverty level would have 
annual savings of at least $294. These savings are particularly 
significant for households whose income is half the poverty level or 
below. For example, a household at 50% of the poverty level would see 
savings of $667.
---------------------------------------------------------------------------

    \102\ The EPA does not have the necessary data to calculate a 
per household surcharge that could increase water bills for higher-
income customers, nor did the EPA include other assistance programs 
in this calculation.
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    However, the effectiveness of the TAP rate structure depends in 
large part on participation by eligible households. When Philadelphia 
launched TAP in 2017, it was estimated that around 60,000 consumers 
would be eligible for the program.\103\ However, as of December 2022, 
only 14,712 households were actively participating in TAP.\104\ Equally 
problematic as low participation rates are the high attrition rates of 
TAP participants. In 2022, 9,496 participants defaulted from TAP due to 
a failure to recertify for the program. Of those who defaulted, 75% 
percent did not respond to the city's request for recertification.\105\ 
Thus, even though Philadelphia enrolled 10,405 participants in 2022, 
the high attrition rate in the program prevents meaningful increases in 
participation. Philadelphia continues outreach efforts to raise 
awareness about TAP; \106\ however, this large gap in participation 
indicates that

[[Page 88336]]

the full potential of the program is likely not being realized.
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    \103\ City of Philadelphia. (2017). Philadelphia Launches New, 
Income-Based, Tiered Assistance Program. Press Release. Office of 
the Mayor. June 20, 2017. https://www.phila.gov/press-releases/mayor/philadelphia-launches-new-income-based-tiered-assistance-program/.
    \104\ City of Philadelphia. (2023). Annual Report to the Mayor 
on the Tiered Assistance Program (TAP). Department of Revenue. March 
31, 2023. https://www.phila.gov/media/20230526113411/Tiered-Assistance-Program-TAP-2022-annual-report.pdf.
    \105\ Id.
    \106\ Id.
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    Based on the structure of TAP and the current low participation 
rates, low-income communities are not necessarily protected from high 
water bills and increasing water rates. The way the program is 
designed, non-TAP customers subsidize the discounts applied to TAP 
customers. When there is high participation, the majority of program 
costs are borne by higher income households and participating low-
income households are protected from high water bills and increasing 
water rates (including potential rate increases to offset costs 
associated with additional wastewater treatment plant technologies). 
With low-participation rates, a higher proportion of low-income 
households are paying the TAP surcharge and face higher water rates, 
thus placing an undue burden on low-income households not participating 
in the program.
    In theory, costs associated with the EPA's proposed rule--if 
partially or fully passed on to residential consumers--should not 
impact the lowest income households in Philadelphia, assuming high 
participation in TAP. However, the current low participation rates in 
TAP indicate that some low-income communities are likely burdened by 
high water bills and could potentially indirectly bear costs associated 
with the EPA's proposed rule. Although Philadelphia's TAP is 
innovative, additional work to increase participation (through 
increased enrollment and decreased attrition rates) can further advance 
water affordability and protect low-income households.
    The example of Philadelphia's TAP illustrates how an income-based 
rate structure can potentially have a measurable impact on low-income 
communities. Municipalities potentially affected by the EPA's proposed 
rule might consider holistic ways to advance water affordability, which 
can include adoption of alternative water rate structures and 
assistance programs that lower water bills for low-income households. 
There are several considerations for municipalities if choosing to 
implement a program similar to TAP in Philadelphia.\107\ An income-
based rate structure, such as Philadelphia's TAP, might be most 
effective for utilities with larger service areas and higher income 
disparities for households within the service area. When a utility has 
a large customer base, it allows the utility to distribute any 
surcharges (to offset lost revenue) among many households.\108\ In 
theory, this redistribution of costs means that the per household 
surcharge can be small and affect higher income households who might be 
less socially vulnerable. In addition, the effectiveness of an income-
based rate structure hinges on the participation rate of low-income 
communities. Municipalities seeking to implement a similar program 
should consider practices to encourage high enrollment and high 
retention rates among qualified households. Such practices could 
include automatically enrolling households who are concurrently on 
other assistance programs (such as SNAP) or ensuring a user-friendly 
process for recertification of eligibility, if applicable. By 
thoughtfully and strategically advancing water affordability programs, 
municipalities can work towards ensuring that socially vulnerable 
communities are not overburdened by expensive water bills.
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    \107\ Mack, E.A., Wrase, S., Dahme, J., Crosby, S.M., Davis, M., 
Wright, M., & Muhammad, R. (2020). An Experiment in Making Water 
Affordable: Philadelphia's Tiered Assistance Program (TAP). Journal 
of the American Water Resources Association, 56(3), 431-449. https://doi.org/10.1111/1752-1688.12830.
    \108\ Id.
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List of Subjects in 40 CFR Part 131

    Environmental protection, Indians-lands, Intergovernmental 
relations, Reporting and recordkeeping requirements, Water pollution 
control.

Michael S. Regan,
Administrator.

    For the reasons set forth in the preamble, the EPA proposes to 
amend 40 CFR part 131 as follows:

PART 131--WATER QUALITY STANDARDS

0
1. The authority citation for part 131 continues to read as follows:

    Authority:  33 U.S.C. 1251 et seq.

0
2. Add Sec.  131.XX to read as follows:


Sec.  131.XX  Water quality standards to protect aquatic life in the 
Delaware River.

    (a) Scope. (1) The designated use in paragraph (b) of this section 
applies to river miles 108.4 to 70.0 of the Delaware River for the 
states of New Jersey and Pennsylvania.
    (2) The aquatic life criteria in paragraph (c) of this section 
apply to river miles 108.4 to 70.0 of the Delaware River for the states 
of Delaware, New Jersey, and Pennsylvania.
    (b) Aquatic life designated use. The aquatic life designated use is 
protection and propagation of resident and migratory aquatic life.
    (c) Dissolved oxygen criteria. The applicable dissolved oxygen 
criteria are shown in table 1 to this paragraph (c).

                               Table 1 to Paragraph (c)--Dissolved Oxygen Criteria
----------------------------------------------------------------------------------------------------------------
                                             Magnitude
                 Season                   (percent oxygen           Duration              Exceedance frequency
                                            saturation)
----------------------------------------------------------------------------------------------------------------
Spawning and Larval Development (March                 66  Daily Average.............  10% (12 Days Cumulative).
 1-June 30).
Juvenile Development (July 1-October                   66  Daily Average.............  10% (12 Days Cumulative).
 31).
                                                       74  Daily Average.............  50% (61 Days Cumulative).
Overwintering (November 1-February 28/                 66  Daily Average.............  10% (12 Days Cumulative).
 29).
----------------------------------------------------------------------------------------------------------------

    (d) Applicability. (1) The aquatic life designated use in paragraph 
(b) of this section applies concurrently with other applicable 
designated uses in New Jersey and Pennsylvania for river miles 108.4 to 
70.0 of the Delaware River.
    (2) The dissolved oxygen aquatic life water quality criteria in 
paragraph (c) of this section are the applicable dissolved oxygen 
criteria in Delaware, New Jersey, and Pennsylvania for river miles 
108.4 to 70.0 of the Delaware River and apply concurrently with 
applicable water quality criteria for other parameters.
    (3) The designated use and criteria established are subject to 
Delaware's, New Jersey's, and Pennsylvania's general rules of 
applicability in the same way and to the same extent as are other 
federally promulgated and state-adopted water quality standards in 
those states.

[FR Doc. 2023-27758 Filed 12-20-23; 8:45 am]
BILLING CODE 6560-50-P


